diff --git a/google/ads/googleads/v3/resources/account_budget.proto b/google/ads/googleads/v3/resources/account_budget.proto
index 11707e86..1b12d891 100644
--- a/google/ads/googleads/v3/resources/account_budget.proto
+++ b/google/ads/googleads/v3/resources/account_budget.proto
@@ -20,6 +20,7 @@ import "google/ads/googleads/v3/enums/account_budget_proposal_type.proto";
 import "google/ads/googleads/v3/enums/account_budget_status.proto";
 import "google/ads/googleads/v3/enums/spending_limit_type.proto";
 import "google/ads/googleads/v3/enums/time_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -60,114 +61,129 @@ message AccountBudget {
   // A pending proposal associated with the enclosing account-level budget,
   // if applicable.
   message PendingAccountBudgetProposal {
-    // The resource name of the proposal.
+    // Output only. The resource name of the proposal.
     // AccountBudgetProposal resource names have the form:
     //
     // `customers/{customer_id}/accountBudgetProposals/{account_budget_proposal_id}`
-    google.protobuf.StringValue account_budget_proposal = 1;
+    google.protobuf.StringValue account_budget_proposal = 1 [
+      (google.api.field_behavior) = OUTPUT_ONLY,
+      (google.api.resource_reference) = {
+        type: "googleads.googleapis.com/AccountBudgetProposal"
+      }
+    ];
 
-    // The type of this proposal, e.g. END to end the budget associated
+    // Output only. The type of this proposal, e.g. END to end the budget associated
     // with this proposal.
-    google.ads.googleads.v3.enums.AccountBudgetProposalTypeEnum.AccountBudgetProposalType proposal_type = 2;
+    google.ads.googleads.v3.enums.AccountBudgetProposalTypeEnum.AccountBudgetProposalType proposal_type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The name to assign to the account-level budget.
-    google.protobuf.StringValue name = 3;
+    // Output only. The name to assign to the account-level budget.
+    google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The start time in yyyy-MM-dd HH:mm:ss format.
-    google.protobuf.StringValue start_date_time = 4;
+    // Output only. The start time in yyyy-MM-dd HH:mm:ss format.
+    google.protobuf.StringValue start_date_time = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // A purchase order number is a value that helps users reference this budget
+    // Output only. A purchase order number is a value that helps users reference this budget
     // in their monthly invoices.
-    google.protobuf.StringValue purchase_order_number = 9;
+    google.protobuf.StringValue purchase_order_number = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Notes associated with this budget.
-    google.protobuf.StringValue notes = 10;
+    // Output only. Notes associated with this budget.
+    google.protobuf.StringValue notes = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The time when this account-level budget proposal was created.
+    // Output only. The time when this account-level budget proposal was created.
     // Formatted as yyyy-MM-dd HH:mm:ss.
-    google.protobuf.StringValue creation_date_time = 11;
+    google.protobuf.StringValue creation_date_time = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
     // The end time of the account-level budget.
     oneof end_time {
-      // The end time in yyyy-MM-dd HH:mm:ss format.
-      google.protobuf.StringValue end_date_time = 5;
+      // Output only. The end time in yyyy-MM-dd HH:mm:ss format.
+      google.protobuf.StringValue end_date_time = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // The end time as a well-defined type, e.g. FOREVER.
-      google.ads.googleads.v3.enums.TimeTypeEnum.TimeType end_time_type = 6;
+      // Output only. The end time as a well-defined type, e.g. FOREVER.
+      google.ads.googleads.v3.enums.TimeTypeEnum.TimeType end_time_type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
     }
 
     // The spending limit.
     oneof spending_limit {
-      // The spending limit in micros.  One million is equivalent to
+      // Output only. The spending limit in micros.  One million is equivalent to
       // one unit.
-      google.protobuf.Int64Value spending_limit_micros = 7;
+      google.protobuf.Int64Value spending_limit_micros = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // The spending limit as a well-defined type, e.g. INFINITE.
-      google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType spending_limit_type = 8;
+      // Output only. The spending limit as a well-defined type, e.g. INFINITE.
+      google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType spending_limit_type = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
     }
   }
 
-  // The resource name of the account-level budget.
+  // Output only. The resource name of the account-level budget.
   // AccountBudget resource names have the form:
   //
   // `customers/{customer_id}/accountBudgets/{account_budget_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AccountBudget"
+    }
+  ];
 
-  // The ID of the account-level budget.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the account-level budget.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the billing setup associated with this account-level
+  // Output only. The resource name of the billing setup associated with this account-level
   // budget.  BillingSetup resource names have the form:
   //
   // `customers/{customer_id}/billingSetups/{billing_setup_id}`
-  google.protobuf.StringValue billing_setup = 3;
+  google.protobuf.StringValue billing_setup = 3 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/BillingSetup"
+    }
+  ];
 
-  // The status of this account-level budget.
-  google.ads.googleads.v3.enums.AccountBudgetStatusEnum.AccountBudgetStatus status = 4;
+  // Output only. The status of this account-level budget.
+  google.ads.googleads.v3.enums.AccountBudgetStatusEnum.AccountBudgetStatus status = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name of the account-level budget.
-  google.protobuf.StringValue name = 5;
+  // Output only. The name of the account-level budget.
+  google.protobuf.StringValue name = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The proposed start time of the account-level budget in
+  // Output only. The proposed start time of the account-level budget in
   // yyyy-MM-dd HH:mm:ss format.  If a start time type of NOW was proposed,
   // this is the time of request.
-  google.protobuf.StringValue proposed_start_date_time = 6;
+  google.protobuf.StringValue proposed_start_date_time = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The approved start time of the account-level budget in yyyy-MM-dd HH:mm:ss
+  // Output only. The approved start time of the account-level budget in yyyy-MM-dd HH:mm:ss
   // format.
   //
   // For example, if a new budget is approved after the proposed start time,
   // the approved start time is the time of approval.
-  google.protobuf.StringValue approved_start_date_time = 7;
+  google.protobuf.StringValue approved_start_date_time = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The total adjustments amount.
+  // Output only. The total adjustments amount.
   //
   // An example of an adjustment is courtesy credits.
-  google.protobuf.Int64Value total_adjustments_micros = 18;
+  google.protobuf.Int64Value total_adjustments_micros = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The value of Ads that have been served, in micros.
+  // Output only. The value of Ads that have been served, in micros.
   //
   // This includes overdelivery costs, in which case a credit might be
   // automatically applied to the budget (see total_adjustments_micros).
-  google.protobuf.Int64Value amount_served_micros = 19;
+  google.protobuf.Int64Value amount_served_micros = 19 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A purchase order number is a value that helps users reference this budget
+  // Output only. A purchase order number is a value that helps users reference this budget
   // in their monthly invoices.
-  google.protobuf.StringValue purchase_order_number = 20;
+  google.protobuf.StringValue purchase_order_number = 20 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Notes associated with the budget.
-  google.protobuf.StringValue notes = 21;
+  // Output only. Notes associated with the budget.
+  google.protobuf.StringValue notes = 21 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The pending proposal to modify this budget, if applicable.
-  PendingAccountBudgetProposal pending_proposal = 22;
+  // Output only. The pending proposal to modify this budget, if applicable.
+  PendingAccountBudgetProposal pending_proposal = 22 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The proposed end time of the account-level budget.
   oneof proposed_end_time {
-    // The proposed end time in yyyy-MM-dd HH:mm:ss format.
-    google.protobuf.StringValue proposed_end_date_time = 8;
+    // Output only. The proposed end time in yyyy-MM-dd HH:mm:ss format.
+    google.protobuf.StringValue proposed_end_date_time = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The proposed end time as a well-defined type, e.g. FOREVER.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_end_time_type = 9;
+    // Output only. The proposed end time as a well-defined type, e.g. FOREVER.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_end_time_type = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The approved end time of the account-level budget.
@@ -175,21 +191,21 @@ message AccountBudget {
   // For example, if a budget's end time is updated and the proposal is approved
   // after the proposed end time, the approved end time is the time of approval.
   oneof approved_end_time {
-    // The approved end time in yyyy-MM-dd HH:mm:ss format.
-    google.protobuf.StringValue approved_end_date_time = 10;
+    // Output only. The approved end time in yyyy-MM-dd HH:mm:ss format.
+    google.protobuf.StringValue approved_end_date_time = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The approved end time as a well-defined type, e.g. FOREVER.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType approved_end_time_type = 11;
+    // Output only. The approved end time as a well-defined type, e.g. FOREVER.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType approved_end_time_type = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The proposed spending limit.
   oneof proposed_spending_limit {
-    // The proposed spending limit in micros.  One million is equivalent to
+    // Output only. The proposed spending limit in micros.  One million is equivalent to
     // one unit.
-    google.protobuf.Int64Value proposed_spending_limit_micros = 12;
+    google.protobuf.Int64Value proposed_spending_limit_micros = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The proposed spending limit as a well-defined type, e.g. INFINITE.
-    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType proposed_spending_limit_type = 13;
+    // Output only. The proposed spending limit as a well-defined type, e.g. INFINITE.
+    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType proposed_spending_limit_type = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The approved spending limit.
@@ -198,15 +214,15 @@ message AccountBudget {
   // proposed spending limit at the time the proposal is approved, the approved
   // spending limit is set to the amount already spent.
   oneof approved_spending_limit {
-    // The approved spending limit in micros.  One million is equivalent to
+    // Output only. The approved spending limit in micros.  One million is equivalent to
     // one unit.  This will only be populated if the proposed spending limit
     // is finite, and will always be greater than or equal to the
     // proposed spending limit.
-    google.protobuf.Int64Value approved_spending_limit_micros = 14;
+    google.protobuf.Int64Value approved_spending_limit_micros = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The approved spending limit as a well-defined type, e.g. INFINITE.  This
+    // Output only. The approved spending limit as a well-defined type, e.g. INFINITE.  This
     // will only be populated if the approved spending limit is INFINITE.
-    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType approved_spending_limit_type = 15;
+    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType approved_spending_limit_type = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The spending limit after adjustments have been applied.  Adjustments are
@@ -214,7 +230,7 @@ message AccountBudget {
   //
   // This value has the final say on how much the account is allowed to spend.
   oneof adjusted_spending_limit {
-    // The adjusted spending limit in micros.  One million is equivalent to
+    // Output only. The adjusted spending limit in micros.  One million is equivalent to
     // one unit.
     //
     // If the approved spending limit is finite, the adjusted
@@ -226,12 +242,12 @@ message AccountBudget {
     //
     // For example, a debit adjustment reduces how much the account is
     // allowed to spend.
-    google.protobuf.Int64Value adjusted_spending_limit_micros = 16;
+    google.protobuf.Int64Value adjusted_spending_limit_micros = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The adjusted spending limit as a well-defined type, e.g. INFINITE.
+    // Output only. The adjusted spending limit as a well-defined type, e.g. INFINITE.
     // This will only be populated if the adjusted spending limit is INFINITE,
     // which is guaranteed to be true if the approved spending limit is
     // INFINITE.
-    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType adjusted_spending_limit_type = 17;
+    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType adjusted_spending_limit_type = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/account_budget_proposal.proto b/google/ads/googleads/v3/resources/account_budget_proposal.proto
index ac376377..5c0c635d 100644
--- a/google/ads/googleads/v3/resources/account_budget_proposal.proto
+++ b/google/ads/googleads/v3/resources/account_budget_proposal.proto
@@ -20,6 +20,7 @@ import "google/ads/googleads/v3/enums/account_budget_proposal_status.proto";
 import "google/ads/googleads/v3/enums/account_budget_proposal_type.proto";
 import "google/ads/googleads/v3/enums/spending_limit_type.proto";
 import "google/ads/googleads/v3/enums/time_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -50,96 +51,111 @@ message AccountBudgetProposal {
     pattern: "customers/{customer}/accountBudgetProposals/{account_budget_proposal}"
   };
 
-  // The resource name of the proposal.
+  // Immutable. The resource name of the proposal.
   // AccountBudgetProposal resource names have the form:
   //
   // `customers/{customer_id}/accountBudgetProposals/{account_budget_proposal_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AccountBudgetProposal"
+    }
+  ];
 
-  // The ID of the proposal.
-  google.protobuf.Int64Value id = 14;
+  // Output only. The ID of the proposal.
+  google.protobuf.Int64Value id = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the billing setup associated with this proposal.
-  google.protobuf.StringValue billing_setup = 2;
+  // Immutable. The resource name of the billing setup associated with this proposal.
+  google.protobuf.StringValue billing_setup = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/BillingSetup"
+    }
+  ];
 
-  // The resource name of the account-level budget associated with this
+  // Immutable. The resource name of the account-level budget associated with this
   // proposal.
-  google.protobuf.StringValue account_budget = 3;
+  google.protobuf.StringValue account_budget = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AccountBudget"
+    }
+  ];
 
-  // The type of this proposal, e.g. END to end the budget associated with this
+  // Immutable. The type of this proposal, e.g. END to end the budget associated with this
   // proposal.
-  google.ads.googleads.v3.enums.AccountBudgetProposalTypeEnum.AccountBudgetProposalType proposal_type = 4;
+  google.ads.googleads.v3.enums.AccountBudgetProposalTypeEnum.AccountBudgetProposalType proposal_type = 4 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The status of this proposal.
+  // Output only. The status of this proposal.
   // When a new proposal is created, the status defaults to PENDING.
-  google.ads.googleads.v3.enums.AccountBudgetProposalStatusEnum.AccountBudgetProposalStatus status = 15;
+  google.ads.googleads.v3.enums.AccountBudgetProposalStatusEnum.AccountBudgetProposalStatus status = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name to assign to the account-level budget.
-  google.protobuf.StringValue proposed_name = 5;
+  // Immutable. The name to assign to the account-level budget.
+  google.protobuf.StringValue proposed_name = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The approved start date time in yyyy-mm-dd hh:mm:ss format.
-  google.protobuf.StringValue approved_start_date_time = 20;
+  // Output only. The approved start date time in yyyy-mm-dd hh:mm:ss format.
+  google.protobuf.StringValue approved_start_date_time = 20 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A purchase order number is a value that enables the user to help them
+  // Immutable. A purchase order number is a value that enables the user to help them
   // reference this budget in their monthly invoices.
-  google.protobuf.StringValue proposed_purchase_order_number = 12;
+  google.protobuf.StringValue proposed_purchase_order_number = 12 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Notes associated with this budget.
-  google.protobuf.StringValue proposed_notes = 13;
+  // Immutable. Notes associated with this budget.
+  google.protobuf.StringValue proposed_notes = 13 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The date time when this account-level budget proposal was created, which is
+  // Output only. The date time when this account-level budget proposal was created, which is
   // not the same as its approval date time, if applicable.
-  google.protobuf.StringValue creation_date_time = 16;
+  google.protobuf.StringValue creation_date_time = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The date time when this account-level budget was approved, if applicable.
-  google.protobuf.StringValue approval_date_time = 17;
+  // Output only. The date time when this account-level budget was approved, if applicable.
+  google.protobuf.StringValue approval_date_time = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The proposed start date time of the account-level budget, which cannot be
   // in the past.
   oneof proposed_start_time {
-    // The proposed start date time in yyyy-mm-dd hh:mm:ss format.
-    google.protobuf.StringValue proposed_start_date_time = 18;
+    // Immutable. The proposed start date time in yyyy-mm-dd hh:mm:ss format.
+    google.protobuf.StringValue proposed_start_date_time = 18 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The proposed start date time as a well-defined type, e.g. NOW.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_start_time_type = 7;
+    // Immutable. The proposed start date time as a well-defined type, e.g. NOW.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_start_time_type = 7 [(google.api.field_behavior) = IMMUTABLE];
   }
 
   // The proposed end date time of the account-level budget, which cannot be in
   // the past.
   oneof proposed_end_time {
-    // The proposed end date time in yyyy-mm-dd hh:mm:ss format.
-    google.protobuf.StringValue proposed_end_date_time = 19;
+    // Immutable. The proposed end date time in yyyy-mm-dd hh:mm:ss format.
+    google.protobuf.StringValue proposed_end_date_time = 19 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The proposed end date time as a well-defined type, e.g. FOREVER.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_end_time_type = 9;
+    // Immutable. The proposed end date time as a well-defined type, e.g. FOREVER.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType proposed_end_time_type = 9 [(google.api.field_behavior) = IMMUTABLE];
   }
 
   // The approved end date time of the account-level budget.
   oneof approved_end_time {
-    // The approved end date time in yyyy-mm-dd hh:mm:ss format.
-    google.protobuf.StringValue approved_end_date_time = 21;
+    // Output only. The approved end date time in yyyy-mm-dd hh:mm:ss format.
+    google.protobuf.StringValue approved_end_date_time = 21 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The approved end date time as a well-defined type, e.g. FOREVER.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType approved_end_time_type = 22;
+    // Output only. The approved end date time as a well-defined type, e.g. FOREVER.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType approved_end_time_type = 22 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The proposed spending limit.
   oneof proposed_spending_limit {
-    // The proposed spending limit in micros.  One million is equivalent to
+    // Immutable. The proposed spending limit in micros.  One million is equivalent to
     // one unit.
-    google.protobuf.Int64Value proposed_spending_limit_micros = 10;
+    google.protobuf.Int64Value proposed_spending_limit_micros = 10 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The proposed spending limit as a well-defined type, e.g. INFINITE.
-    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType proposed_spending_limit_type = 11;
+    // Immutable. The proposed spending limit as a well-defined type, e.g. INFINITE.
+    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType proposed_spending_limit_type = 11 [(google.api.field_behavior) = IMMUTABLE];
   }
 
   // The approved spending limit.
   oneof approved_spending_limit {
-    // The approved spending limit in micros.  One million is equivalent to
+    // Output only. The approved spending limit in micros.  One million is equivalent to
     // one unit.
-    google.protobuf.Int64Value approved_spending_limit_micros = 23;
+    google.protobuf.Int64Value approved_spending_limit_micros = 23 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The approved spending limit as a well-defined type, e.g. INFINITE.
-    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType approved_spending_limit_type = 24;
+    // Output only. The approved spending limit as a well-defined type, e.g. INFINITE.
+    google.ads.googleads.v3.enums.SpendingLimitTypeEnum.SpendingLimitType approved_spending_limit_type = 24 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/ad.proto b/google/ads/googleads/v3/resources/ad.proto
index 3c5e3aac..04705eef 100644
--- a/google/ads/googleads/v3/resources/ad.proto
+++ b/google/ads/googleads/v3/resources/ad.proto
@@ -23,6 +23,7 @@ import "google/ads/googleads/v3/common/url_collection.proto";
 import "google/ads/googleads/v3/enums/ad_type.proto";
 import "google/ads/googleads/v3/enums/device.proto";
 import "google/ads/googleads/v3/enums/system_managed_entity_source.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -45,14 +46,19 @@ message Ad {
     pattern: "customers/{customer}/ads/{ad}"
   };
 
-  // The resource name of the ad.
+  // Immutable. The resource name of the ad.
   // Ad resource names have the form:
   //
   // `customers/{customer_id}/ads/{ad_id}`
-  string resource_name = 37;
+  string resource_name = 37 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Ad"
+    }
+  ];
 
-  // The ID of the ad.
-  google.protobuf.Int64Value id = 1;
+  // Output only. The ID of the ad.
+  google.protobuf.Int64Value id = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The list of possible final URLs after all cross-domain redirects for the
   // ad.
@@ -79,14 +85,14 @@ message Ad {
   // The URL that appears in the ad description for some ad formats.
   google.protobuf.StringValue display_url = 4;
 
-  // The type of ad.
-  google.ads.googleads.v3.enums.AdTypeEnum.AdType type = 5;
+  // Output only. The type of ad.
+  google.ads.googleads.v3.enums.AdTypeEnum.AdType type = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Indicates if this ad was automatically added by Google Ads and not by a
+  // Output only. Indicates if this ad was automatically added by Google Ads and not by a
   // user. For example, this could happen when ads are automatically created as
   // suggestions for new ads based on knowledge of how existing ads are
   // performing.
-  google.protobuf.BoolValue added_by_google_ads = 19;
+  google.protobuf.BoolValue added_by_google_ads = 19 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The device preference for the ad. You can only specify a preference for
   // mobile devices. When this preference is set the ad will be preferred over
@@ -100,13 +106,13 @@ message Ad {
   // can be referenced from other fields in the ad.
   repeated google.ads.googleads.v3.common.UrlCollection url_collections = 26;
 
-  // The name of the ad. This is only used to be able to identify the ad. It
+  // Immutable. The name of the ad. This is only used to be able to identify the ad. It
   // does not need to be unique and does not affect the served ad.
-  google.protobuf.StringValue name = 23;
+  google.protobuf.StringValue name = 23 [(google.api.field_behavior) = IMMUTABLE];
 
-  // If this ad is system managed, then this field will indicate the source.
+  // Output only. If this ad is system managed, then this field will indicate the source.
   // This field is read-only.
-  google.ads.googleads.v3.enums.SystemManagedResourceSourceEnum.SystemManagedResourceSource system_managed_resource_source = 27;
+  google.ads.googleads.v3.enums.SystemManagedResourceSourceEnum.SystemManagedResourceSource system_managed_resource_source = 27 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Details pertinent to the ad type. Exactly one value must be set.
   oneof ad_data {
@@ -153,8 +159,8 @@ message Ad {
     // Details pertaining to an app ad.
     google.ads.googleads.v3.common.AppAdInfo app_ad = 29;
 
-    // Details pertaining to a legacy app install ad.
-    google.ads.googleads.v3.common.LegacyAppInstallAdInfo legacy_app_install_ad = 30;
+    // Immutable. Details pertaining to a legacy app install ad.
+    google.ads.googleads.v3.common.LegacyAppInstallAdInfo legacy_app_install_ad = 30 [(google.api.field_behavior) = IMMUTABLE];
 
     // Details pertaining to a responsive display ad.
     google.ads.googleads.v3.common.ResponsiveDisplayAdInfo responsive_display_ad = 31;
diff --git a/google/ads/googleads/v3/resources/ad_group.proto b/google/ads/googleads/v3/resources/ad_group.proto
index 8af2829c..271f2954 100644
--- a/google/ads/googleads/v3/resources/ad_group.proto
+++ b/google/ads/googleads/v3/resources/ad_group.proto
@@ -24,6 +24,7 @@ import "google/ads/googleads/v3/enums/ad_group_status.proto";
 import "google/ads/googleads/v3/enums/ad_group_type.proto";
 import "google/ads/googleads/v3/enums/bidding_source.proto";
 import "google/ads/googleads/v3/enums/targeting_dimension.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -46,14 +47,19 @@ message AdGroup {
     pattern: "customers/{customer}/adGroups/{ad_group}"
   };
 
-  // The resource name of the ad group.
+  // Immutable. The resource name of the ad group.
   // Ad group resource names have the form:
   //
   // `customers/{customer_id}/adGroups/{ad_group_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // The ID of the ad group.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the ad group.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the ad group.
   //
@@ -69,20 +75,25 @@ message AdGroup {
   // The status of the ad group.
   google.ads.googleads.v3.enums.AdGroupStatusEnum.AdGroupStatus status = 5;
 
-  // The type of the ad group.
-  google.ads.googleads.v3.enums.AdGroupTypeEnum.AdGroupType type = 12;
+  // Immutable. The type of the ad group.
+  google.ads.googleads.v3.enums.AdGroupTypeEnum.AdGroupType type = 12 [(google.api.field_behavior) = IMMUTABLE];
 
   // The ad rotation mode of the ad group.
   google.ads.googleads.v3.enums.AdGroupAdRotationModeEnum.AdGroupAdRotationMode ad_rotation_mode = 22;
 
-  // For draft or experiment ad groups, this field is the resource name of the
+  // Output only. For draft or experiment ad groups, this field is the resource name of the
   // base ad group from which this ad group was created. If a draft or
   // experiment ad group does not have a base ad group, then this field is null.
   //
   // For base ad groups, this field equals the ad group resource name.
   //
   // This field is read-only.
-  google.protobuf.StringValue base_ad_group = 18;
+  google.protobuf.StringValue base_ad_group = 18 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
   // The URL template for constructing a tracking URL.
   google.protobuf.StringValue tracking_url_template = 13;
@@ -91,8 +102,13 @@ message AdGroup {
   // `tracking_url_template`, `final_urls`, or `mobile_final_urls`.
   repeated google.ads.googleads.v3.common.CustomParameter url_custom_parameters = 6;
 
-  // The campaign to which the ad group belongs.
-  google.protobuf.StringValue campaign = 10;
+  // Immutable. The campaign to which the ad group belongs.
+  google.protobuf.StringValue campaign = 10 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
   // The maximum CPC (cost-per-click) bid.
   google.protobuf.Int64Value cpc_bid_micros = 14;
@@ -103,8 +119,8 @@ message AdGroup {
   // The target CPA (cost-per-acquisition).
   google.protobuf.Int64Value target_cpa_micros = 27;
 
-  // The CPV (cost-per-view) bid.
-  google.protobuf.Int64Value cpv_bid_micros = 17;
+  // Output only. The CPV (cost-per-view) bid.
+  google.protobuf.Int64Value cpv_bid_micros = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Average amount in micros that the advertiser is willing to pay for every
   // thousand times the ad is shown.
@@ -135,22 +151,27 @@ message AdGroup {
   // Setting for targeting related features.
   google.ads.googleads.v3.common.TargetingSetting targeting_setting = 25;
 
-  // The effective target CPA (cost-per-acquisition).
+  // Output only. The effective target CPA (cost-per-acquisition).
   // This field is read-only.
-  google.protobuf.Int64Value effective_target_cpa_micros = 28;
+  google.protobuf.Int64Value effective_target_cpa_micros = 28 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective target CPA.
+  // Output only. Source of the effective target CPA.
   // This field is read-only.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_target_cpa_source = 29;
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_target_cpa_source = 29 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The effective target ROAS (return-on-ad-spend).
+  // Output only. The effective target ROAS (return-on-ad-spend).
   // This field is read-only.
-  google.protobuf.DoubleValue effective_target_roas = 31;
+  google.protobuf.DoubleValue effective_target_roas = 31 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective target ROAS.
+  // Output only. Source of the effective target ROAS.
   // This field is read-only.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_target_roas_source = 32;
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_target_roas_source = 32 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource names of labels attached to this ad group.
-  repeated google.protobuf.StringValue labels = 33;
+  // Output only. The resource names of labels attached to this ad group.
+  repeated google.protobuf.StringValue labels = 33 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupLabel"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_ad.proto b/google/ads/googleads/v3/resources/ad_group_ad.proto
index d1432dae..3210f075 100644
--- a/google/ads/googleads/v3/resources/ad_group_ad.proto
+++ b/google/ads/googleads/v3/resources/ad_group_ad.proto
@@ -22,6 +22,7 @@ import "google/ads/googleads/v3/enums/ad_strength.proto";
 import "google/ads/googleads/v3/enums/policy_approval_status.proto";
 import "google/ads/googleads/v3/enums/policy_review_status.proto";
 import "google/ads/googleads/v3/resources/ad.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -44,37 +45,47 @@ message AdGroupAd {
     pattern: "customers/{customer}/adGroupAds/{ad_group_ad}"
   };
 
-  // The resource name of the ad.
+  // Immutable. The resource name of the ad.
   // Ad group ad resource names have the form:
   //
   // `customers/{customer_id}/adGroupAds/{ad_group_id}~{ad_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAd"
+    }
+  ];
 
   // The status of the ad.
   google.ads.googleads.v3.enums.AdGroupAdStatusEnum.AdGroupAdStatus status = 3;
 
-  // The ad group to which the ad belongs.
-  google.protobuf.StringValue ad_group = 4;
+  // Immutable. The ad group to which the ad belongs.
+  google.protobuf.StringValue ad_group = 4 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // The ad.
-  Ad ad = 5;
+  // Immutable. The ad.
+  Ad ad = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Policy information for the ad.
-  AdGroupAdPolicySummary policy_summary = 6;
+  // Output only. Policy information for the ad.
+  AdGroupAdPolicySummary policy_summary = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Overall ad strength for this ad group ad.
-  google.ads.googleads.v3.enums.AdStrengthEnum.AdStrength ad_strength = 7;
+  // Output only. Overall ad strength for this ad group ad.
+  google.ads.googleads.v3.enums.AdStrengthEnum.AdStrength ad_strength = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Contains policy information for an ad.
 message AdGroupAdPolicySummary {
-  // The list of policy findings for this ad.
-  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 1;
+  // Output only. The list of policy findings for this ad.
+  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Where in the review process this ad is.
-  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 2;
+  // Output only. Where in the review process this ad is.
+  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The overall approval status of this ad, calculated based on the status of
+  // Output only. The overall approval status of this ad, calculated based on the status of
   // its individual policy topic entries.
-  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 3;
+  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_ad_asset_view.proto b/google/ads/googleads/v3/resources/ad_group_ad_asset_view.proto
index 5ab7f378..624228af 100644
--- a/google/ads/googleads/v3/resources/ad_group_ad_asset_view.proto
+++ b/google/ads/googleads/v3/resources/ad_group_ad_asset_view.proto
@@ -21,6 +21,7 @@ import "google/ads/googleads/v3/enums/asset_field_type.proto";
 import "google/ads/googleads/v3/enums/asset_performance_label.proto";
 import "google/ads/googleads/v3/enums/policy_approval_status.proto";
 import "google/ads/googleads/v3/enums/policy_review_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,37 +44,52 @@ message AdGroupAdAssetView {
     pattern: "customers/{customer}/adGroupAdAssets/{ad_group_ad_asset_view}"
   };
 
-  // The resource name of the ad group ad asset view.
+  // Output only. The resource name of the ad group ad asset view.
   // Ad group ad asset view resource names have the form:
   //
   // `customers/{customer_id}/adGroupAdAssets/{AdGroupAdAsset.ad_group_id}~{AdGroupAdAsset.ad.ad_id}~{AdGroupAdAsset.asset_id}~{AdGroupAdAsset.asset_field_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAdAssetView"
+    }
+  ];
 
-  // The ad group ad to which the asset is linked.
-  google.protobuf.StringValue ad_group_ad = 5;
+  // Output only. The ad group ad to which the asset is linked.
+  google.protobuf.StringValue ad_group_ad = 5 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAd"
+    }
+  ];
 
-  // The asset which is linked to the ad group ad.
-  google.protobuf.StringValue asset = 6;
+  // Output only. The asset which is linked to the ad group ad.
+  google.protobuf.StringValue asset = 6 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Asset"
+    }
+  ];
 
-  // Role that the asset takes in the ad.
-  google.ads.googleads.v3.enums.AssetFieldTypeEnum.AssetFieldType field_type = 2;
+  // Output only. Role that the asset takes in the ad.
+  google.ads.googleads.v3.enums.AssetFieldTypeEnum.AssetFieldType field_type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Policy information for the ad group ad asset.
-  AdGroupAdAssetPolicySummary policy_summary = 3;
+  // Output only. Policy information for the ad group ad asset.
+  AdGroupAdAssetPolicySummary policy_summary = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Performance of an asset linkage.
-  google.ads.googleads.v3.enums.AssetPerformanceLabelEnum.AssetPerformanceLabel performance_label = 4;
+  // Output only. Performance of an asset linkage.
+  google.ads.googleads.v3.enums.AssetPerformanceLabelEnum.AssetPerformanceLabel performance_label = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Contains policy information for an ad group ad asset.
 message AdGroupAdAssetPolicySummary {
-  // The list of policy findings for the ad group ad asset.
-  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 1;
+  // Output only. The list of policy findings for the ad group ad asset.
+  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Where in the review process this ad group ad asset is.
-  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 2;
+  // Output only. Where in the review process this ad group ad asset is.
+  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The overall approval status of this ad group ad asset, calculated based on
+  // Output only. The overall approval status of this ad group ad asset, calculated based on
   // the status of its individual policy topic entries.
-  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 3;
+  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_ad_label.proto b/google/ads/googleads/v3/resources/ad_group_ad_label.proto
index 8a027220..21e1f671 100644
--- a/google/ads/googleads/v3/resources/ad_group_ad_label.proto
+++ b/google/ads/googleads/v3/resources/ad_group_ad_label.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,14 +39,29 @@ message AdGroupAdLabel {
     pattern: "customers/{customer}/adGroupAdLabels/{ad_group_ad_label}"
   };
 
-  // The resource name of the ad group ad label.
+  // Immutable. The resource name of the ad group ad label.
   // Ad group ad label resource names have the form:
   // `customers/{customer_id}/adGroupAdLabels/{ad_group_id}~{ad_id}~{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAdLabel"
+    }
+  ];
 
-  // The ad group ad to which the label is attached.
-  google.protobuf.StringValue ad_group_ad = 2;
+  // Immutable. The ad group ad to which the label is attached.
+  google.protobuf.StringValue ad_group_ad = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAd"
+    }
+  ];
 
-  // The label assigned to the ad group ad.
-  google.protobuf.StringValue label = 3;
+  // Immutable. The label assigned to the ad group ad.
+  google.protobuf.StringValue label = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Label"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_audience_view.proto b/google/ads/googleads/v3/resources/ad_group_audience_view.proto
index 0c1f96a1..db25b812 100644
--- a/google/ads/googleads/v3/resources/ad_group_audience_view.proto
+++ b/google/ads/googleads/v3/resources/ad_group_audience_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -40,9 +41,14 @@ message AdGroupAudienceView {
     pattern: "customers/{customer}/adGroupAudienceViews/{ad_group_audience_view}"
   };
 
-  // The resource name of the ad group audience view.
+  // Output only. The resource name of the ad group audience view.
   // Ad group audience view resource names have the form:
   //
   // `customers/{customer_id}/adGroupAudienceViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAudienceView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_bid_modifier.proto b/google/ads/googleads/v3/resources/ad_group_bid_modifier.proto
index 17ac4e1a..0590f64f 100644
--- a/google/ads/googleads/v3/resources/ad_group_bid_modifier.proto
+++ b/google/ads/googleads/v3/resources/ad_group_bid_modifier.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/criteria.proto";
 import "google/ads/googleads/v3/enums/bid_modifier_source.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,53 +41,68 @@ message AdGroupBidModifier {
     pattern: "customers/{customer}/adGroupBidModifiers/{ad_group_bid_modifier}"
   };
 
-  // The resource name of the ad group bid modifier.
+  // Immutable. The resource name of the ad group bid modifier.
   // Ad group bid modifier resource names have the form:
   //
   // `customers/{customer_id}/adGroupBidModifiers/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupBidModifier"
+    }
+  ];
 
-  // The ad group to which this criterion belongs.
-  google.protobuf.StringValue ad_group = 2;
+  // Immutable. The ad group to which this criterion belongs.
+  google.protobuf.StringValue ad_group = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // The ID of the criterion to bid modify.
+  // Output only. The ID of the criterion to bid modify.
   //
   // This field is ignored for mutates.
-  google.protobuf.Int64Value criterion_id = 3;
+  google.protobuf.Int64Value criterion_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The modifier for the bid when the criterion matches. The modifier must be
   // in the range: 0.1 - 10.0. The range is 1.0 - 6.0 for PreferredContent.
   // Use 0 to opt out of a Device type.
   google.protobuf.DoubleValue bid_modifier = 4;
 
-  // The base ad group from which this draft/trial adgroup bid modifier was
+  // Output only. The base ad group from which this draft/trial adgroup bid modifier was
   // created. If ad_group is a base ad group then this field will be equal to
   // ad_group. If the ad group was created in the draft or trial and has no
   // corresponding base ad group, then this field will be null.
   // This field is readonly.
-  google.protobuf.StringValue base_ad_group = 9;
+  google.protobuf.StringValue base_ad_group = 9 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // Bid modifier source.
-  google.ads.googleads.v3.enums.BidModifierSourceEnum.BidModifierSource bid_modifier_source = 10;
+  // Output only. Bid modifier source.
+  google.ads.googleads.v3.enums.BidModifierSourceEnum.BidModifierSource bid_modifier_source = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The criterion of this ad group bid modifier.
   oneof criterion {
-    // Criterion for hotel date selection (default dates vs. user selected).
-    google.ads.googleads.v3.common.HotelDateSelectionTypeInfo hotel_date_selection_type = 5;
+    // Immutable. Criterion for hotel date selection (default dates vs. user selected).
+    google.ads.googleads.v3.common.HotelDateSelectionTypeInfo hotel_date_selection_type = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Criterion for number of days prior to the stay the booking is being made.
-    google.ads.googleads.v3.common.HotelAdvanceBookingWindowInfo hotel_advance_booking_window = 6;
+    // Immutable. Criterion for number of days prior to the stay the booking is being made.
+    google.ads.googleads.v3.common.HotelAdvanceBookingWindowInfo hotel_advance_booking_window = 6 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Criterion for length of hotel stay in nights.
-    google.ads.googleads.v3.common.HotelLengthOfStayInfo hotel_length_of_stay = 7;
+    // Immutable. Criterion for length of hotel stay in nights.
+    google.ads.googleads.v3.common.HotelLengthOfStayInfo hotel_length_of_stay = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Criterion for day of the week the booking is for.
-    google.ads.googleads.v3.common.HotelCheckInDayInfo hotel_check_in_day = 8;
+    // Immutable. Criterion for day of the week the booking is for.
+    google.ads.googleads.v3.common.HotelCheckInDayInfo hotel_check_in_day = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-    // A device criterion.
-    google.ads.googleads.v3.common.DeviceInfo device = 11;
+    // Immutable. A device criterion.
+    google.ads.googleads.v3.common.DeviceInfo device = 11 [(google.api.field_behavior) = IMMUTABLE];
 
-    // A preferred content criterion.
-    google.ads.googleads.v3.common.PreferredContentInfo preferred_content = 12;
+    // Immutable. A preferred content criterion.
+    google.ads.googleads.v3.common.PreferredContentInfo preferred_content = 12 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_criterion.proto b/google/ads/googleads/v3/resources/ad_group_criterion.proto
index 799fe4dd..c992cf2d 100644
--- a/google/ads/googleads/v3/resources/ad_group_criterion.proto
+++ b/google/ads/googleads/v3/resources/ad_group_criterion.proto
@@ -24,6 +24,7 @@ import "google/ads/googleads/v3/enums/bidding_source.proto";
 import "google/ads/googleads/v3/enums/criterion_system_serving_status.proto";
 import "google/ads/googleads/v3/enums/criterion_type.proto";
 import "google/ads/googleads/v3/enums/quality_score_bucket.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -48,79 +49,89 @@ message AdGroupCriterion {
 
   // A container for ad group criterion quality information.
   message QualityInfo {
-    // The quality score.
+    // Output only. The quality score.
     //
     // This field may not be populated if Google does not have enough
     // information to determine a value.
-    google.protobuf.Int32Value quality_score = 1;
+    google.protobuf.Int32Value quality_score = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The performance of the ad compared to other advertisers.
-    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket creative_quality_score = 2;
+    // Output only. The performance of the ad compared to other advertisers.
+    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket creative_quality_score = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The quality score of the landing page.
-    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket post_click_quality_score = 3;
+    // Output only. The quality score of the landing page.
+    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket post_click_quality_score = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The click-through rate compared to that of other advertisers.
-    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket search_predicted_ctr = 4;
+    // Output only. The click-through rate compared to that of other advertisers.
+    google.ads.googleads.v3.enums.QualityScoreBucketEnum.QualityScoreBucket search_predicted_ctr = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // Estimates for criterion bids at various positions.
   message PositionEstimates {
-    // The estimate of the CPC bid required for ad to be shown on first
+    // Output only. The estimate of the CPC bid required for ad to be shown on first
     // page of search results.
-    google.protobuf.Int64Value first_page_cpc_micros = 1;
+    google.protobuf.Int64Value first_page_cpc_micros = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The estimate of the CPC bid required for ad to be displayed in first
+    // Output only. The estimate of the CPC bid required for ad to be displayed in first
     // position, at the top of the first page of search results.
-    google.protobuf.Int64Value first_position_cpc_micros = 2;
+    google.protobuf.Int64Value first_position_cpc_micros = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The estimate of the CPC bid required for ad to be displayed at the top
+    // Output only. The estimate of the CPC bid required for ad to be displayed at the top
     // of the first page of search results.
-    google.protobuf.Int64Value top_of_page_cpc_micros = 3;
+    google.protobuf.Int64Value top_of_page_cpc_micros = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Estimate of how many clicks per week you might get by changing your
+    // Output only. Estimate of how many clicks per week you might get by changing your
     // keyword bid to the value in first_position_cpc_micros.
-    google.protobuf.Int64Value estimated_add_clicks_at_first_position_cpc = 4;
+    google.protobuf.Int64Value estimated_add_clicks_at_first_position_cpc = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Estimate of how your cost per week might change when changing your
+    // Output only. Estimate of how your cost per week might change when changing your
     // keyword bid to the value in first_position_cpc_micros.
-    google.protobuf.Int64Value estimated_add_cost_at_first_position_cpc = 5;
+    google.protobuf.Int64Value estimated_add_cost_at_first_position_cpc = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The resource name of the ad group criterion.
+  // Immutable. The resource name of the ad group criterion.
   // Ad group criterion resource names have the form:
   //
   // `customers/{customer_id}/adGroupCriteria/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterion"
+    }
+  ];
 
-  // The ID of the criterion.
+  // Output only. The ID of the criterion.
   //
   // This field is ignored for mutates.
-  google.protobuf.Int64Value criterion_id = 26;
+  google.protobuf.Int64Value criterion_id = 26 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The status of the criterion.
   google.ads.googleads.v3.enums.AdGroupCriterionStatusEnum.AdGroupCriterionStatus status = 3;
 
-  // Information regarding the quality of the criterion.
-  QualityInfo quality_info = 4;
+  // Output only. Information regarding the quality of the criterion.
+  QualityInfo quality_info = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ad group to which the criterion belongs.
-  google.protobuf.StringValue ad_group = 5;
+  // Immutable. The ad group to which the criterion belongs.
+  google.protobuf.StringValue ad_group = 5 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // The type of the criterion.
-  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 25;
+  // Output only. The type of the criterion.
+  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 25 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether to target (`false`) or exclude (`true`) the criterion.
+  // Immutable. Whether to target (`false`) or exclude (`true`) the criterion.
   //
   // This field is immutable. To switch a criterion from positive to negative,
   // remove then re-add it.
-  google.protobuf.BoolValue negative = 31;
+  google.protobuf.BoolValue negative = 31 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Serving status of the criterion.
-  google.ads.googleads.v3.enums.CriterionSystemServingStatusEnum.CriterionSystemServingStatus system_serving_status = 52;
+  // Output only. Serving status of the criterion.
+  google.ads.googleads.v3.enums.CriterionSystemServingStatusEnum.CriterionSystemServingStatus system_serving_status = 52 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Approval status of the criterion.
-  google.ads.googleads.v3.enums.AdGroupCriterionApprovalStatusEnum.AdGroupCriterionApprovalStatus approval_status = 53;
+  // Output only. Approval status of the criterion.
+  google.ads.googleads.v3.enums.AdGroupCriterionApprovalStatusEnum.AdGroupCriterionApprovalStatus approval_status = 53 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The modifier for the bid when the criterion matches. The modifier must be
   // in the range: 0.1 - 10.0. Most targetable criteria types support modifiers.
@@ -140,32 +151,32 @@ message AdGroupCriterion {
   // value stored here is 1,000,000 * [fraction].
   google.protobuf.Int64Value percent_cpc_bid_micros = 33;
 
-  // The effective CPC (cost-per-click) bid.
-  google.protobuf.Int64Value effective_cpc_bid_micros = 18;
+  // Output only. The effective CPC (cost-per-click) bid.
+  google.protobuf.Int64Value effective_cpc_bid_micros = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The effective CPM (cost-per-thousand viewable impressions) bid.
-  google.protobuf.Int64Value effective_cpm_bid_micros = 19;
+  // Output only. The effective CPM (cost-per-thousand viewable impressions) bid.
+  google.protobuf.Int64Value effective_cpm_bid_micros = 19 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The effective CPV (cost-per-view) bid.
-  google.protobuf.Int64Value effective_cpv_bid_micros = 20;
+  // Output only. The effective CPV (cost-per-view) bid.
+  google.protobuf.Int64Value effective_cpv_bid_micros = 20 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The effective Percent CPC bid amount.
-  google.protobuf.Int64Value effective_percent_cpc_bid_micros = 34;
+  // Output only. The effective Percent CPC bid amount.
+  google.protobuf.Int64Value effective_percent_cpc_bid_micros = 34 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective CPC bid.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpc_bid_source = 21;
+  // Output only. Source of the effective CPC bid.
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpc_bid_source = 21 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective CPM bid.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpm_bid_source = 22;
+  // Output only. Source of the effective CPM bid.
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpm_bid_source = 22 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective CPV bid.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpv_bid_source = 23;
+  // Output only. Source of the effective CPV bid.
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_cpv_bid_source = 23 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Source of the effective Percent CPC bid.
-  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_percent_cpc_bid_source = 35;
+  // Output only. Source of the effective Percent CPC bid.
+  google.ads.googleads.v3.enums.BiddingSourceEnum.BiddingSource effective_percent_cpc_bid_source = 35 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Estimates for criterion bids at various positions.
-  PositionEstimates position_estimates = 10;
+  // Output only. Estimates for criterion bids at various positions.
+  PositionEstimates position_estimates = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The list of possible final URLs after all cross-domain redirects for the
   // ad.
@@ -188,58 +199,58 @@ message AdGroupCriterion {
   //
   // Exactly one must be set.
   oneof criterion {
-    // Keyword.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 27;
+    // Immutable. Keyword.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 27 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Placement.
-    google.ads.googleads.v3.common.PlacementInfo placement = 28;
+    // Immutable. Placement.
+    google.ads.googleads.v3.common.PlacementInfo placement = 28 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile app category.
-    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 29;
+    // Immutable. Mobile app category.
+    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 29 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile application.
-    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 30;
+    // Immutable. Mobile application.
+    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 30 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Listing group.
-    google.ads.googleads.v3.common.ListingGroupInfo listing_group = 32;
+    // Immutable. Listing group.
+    google.ads.googleads.v3.common.ListingGroupInfo listing_group = 32 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Age range.
-    google.ads.googleads.v3.common.AgeRangeInfo age_range = 36;
+    // Immutable. Age range.
+    google.ads.googleads.v3.common.AgeRangeInfo age_range = 36 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Gender.
-    google.ads.googleads.v3.common.GenderInfo gender = 37;
+    // Immutable. Gender.
+    google.ads.googleads.v3.common.GenderInfo gender = 37 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Income range.
-    google.ads.googleads.v3.common.IncomeRangeInfo income_range = 38;
+    // Immutable. Income range.
+    google.ads.googleads.v3.common.IncomeRangeInfo income_range = 38 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Parental status.
-    google.ads.googleads.v3.common.ParentalStatusInfo parental_status = 39;
+    // Immutable. Parental status.
+    google.ads.googleads.v3.common.ParentalStatusInfo parental_status = 39 [(google.api.field_behavior) = IMMUTABLE];
 
-    // User List.
-    google.ads.googleads.v3.common.UserListInfo user_list = 42;
+    // Immutable. User List.
+    google.ads.googleads.v3.common.UserListInfo user_list = 42 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Video.
-    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 40;
+    // Immutable. YouTube Video.
+    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 40 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Channel.
-    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 41;
+    // Immutable. YouTube Channel.
+    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 41 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Topic.
-    google.ads.googleads.v3.common.TopicInfo topic = 43;
+    // Immutable. Topic.
+    google.ads.googleads.v3.common.TopicInfo topic = 43 [(google.api.field_behavior) = IMMUTABLE];
 
-    // User Interest.
-    google.ads.googleads.v3.common.UserInterestInfo user_interest = 45;
+    // Immutable. User Interest.
+    google.ads.googleads.v3.common.UserInterestInfo user_interest = 45 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Webpage
-    google.ads.googleads.v3.common.WebpageInfo webpage = 46;
+    // Immutable. Webpage
+    google.ads.googleads.v3.common.WebpageInfo webpage = 46 [(google.api.field_behavior) = IMMUTABLE];
 
-    // App Payment Model.
-    google.ads.googleads.v3.common.AppPaymentModelInfo app_payment_model = 47;
+    // Immutable. App Payment Model.
+    google.ads.googleads.v3.common.AppPaymentModelInfo app_payment_model = 47 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Custom Affinity.
-    google.ads.googleads.v3.common.CustomAffinityInfo custom_affinity = 48;
+    // Immutable. Custom Affinity.
+    google.ads.googleads.v3.common.CustomAffinityInfo custom_affinity = 48 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Custom Intent.
-    google.ads.googleads.v3.common.CustomIntentInfo custom_intent = 49;
+    // Immutable. Custom Intent.
+    google.ads.googleads.v3.common.CustomIntentInfo custom_intent = 49 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_criterion_label.proto b/google/ads/googleads/v3/resources/ad_group_criterion_label.proto
index 8c34c5d7..54b13167 100644
--- a/google/ads/googleads/v3/resources/ad_group_criterion_label.proto
+++ b/google/ads/googleads/v3/resources/ad_group_criterion_label.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,14 +39,29 @@ message AdGroupCriterionLabel {
     pattern: "customers/{customer}/adGroupCriterionLabels/{ad_group_criterion_label}"
   };
 
-  // The resource name of the ad group criterion label.
+  // Immutable. The resource name of the ad group criterion label.
   // Ad group criterion label resource names have the form:
   // `customers/{customer_id}/adGroupCriterionLabels/{ad_group_id}~{criterion_id}~{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterionLabel"
+    }
+  ];
 
-  // The ad group criterion to which the label is attached.
-  google.protobuf.StringValue ad_group_criterion = 2;
+  // Immutable. The ad group criterion to which the label is attached.
+  google.protobuf.StringValue ad_group_criterion = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterion"
+    }
+  ];
 
-  // The label assigned to the ad group criterion.
-  google.protobuf.StringValue label = 3;
+  // Immutable. The label assigned to the ad group criterion.
+  google.protobuf.StringValue label = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Label"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_criterion_simulation.proto b/google/ads/googleads/v3/resources/ad_group_criterion_simulation.proto
index 70cf0c73..4b5e7315 100644
--- a/google/ads/googleads/v3/resources/ad_group_criterion_simulation.proto
+++ b/google/ads/googleads/v3/resources/ad_group_criterion_simulation.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/simulation.proto";
 import "google/ads/googleads/v3/enums/simulation_modification_method.proto";
 import "google/ads/googleads/v3/enums/simulation_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -47,33 +48,38 @@ message AdGroupCriterionSimulation {
     pattern: "customers/{customer}/adGroupCriterionSimulations/{ad_group_criterion_simulation}"
   };
 
-  // The resource name of the ad group criterion simulation.
+  // Output only. The resource name of the ad group criterion simulation.
   // Ad group criterion simulation resource names have the form:
   //
   // `customers/{customer_id}/adGroupCriterionSimulations/{ad_group_id}~{criterion_id}~{type}~{modification_method}~{start_date}~{end_date}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterionSimulation"
+    }
+  ];
 
-  // AdGroup ID of the simulation.
-  google.protobuf.Int64Value ad_group_id = 2;
+  // Output only. AdGroup ID of the simulation.
+  google.protobuf.Int64Value ad_group_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Criterion ID of the simulation.
-  google.protobuf.Int64Value criterion_id = 3;
+  // Output only. Criterion ID of the simulation.
+  google.protobuf.Int64Value criterion_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The field that the simulation modifies.
-  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 4;
+  // Output only. The field that the simulation modifies.
+  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // How the simulation modifies the field.
-  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 5;
+  // Output only. How the simulation modifies the field.
+  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // First day on which the simulation is based, in YYYY-MM-DD format.
-  google.protobuf.StringValue start_date = 6;
+  // Output only. First day on which the simulation is based, in YYYY-MM-DD format.
+  google.protobuf.StringValue start_date = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Last day on which the simulation is based, in YYYY-MM-DD format.
-  google.protobuf.StringValue end_date = 7;
+  // Output only. Last day on which the simulation is based, in YYYY-MM-DD format.
+  google.protobuf.StringValue end_date = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // List of simulation points.
   oneof point_list {
-    // Simulation points if the simulation type is CPC_BID.
-    google.ads.googleads.v3.common.CpcBidSimulationPointList cpc_bid_point_list = 8;
+    // Output only. Simulation points if the simulation type is CPC_BID.
+    google.ads.googleads.v3.common.CpcBidSimulationPointList cpc_bid_point_list = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_extension_setting.proto b/google/ads/googleads/v3/resources/ad_group_extension_setting.proto
index e1fa2388..5dabbcf4 100644
--- a/google/ads/googleads/v3/resources/ad_group_extension_setting.proto
+++ b/google/ads/googleads/v3/resources/ad_group_extension_setting.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/extension_setting_device.proto";
 import "google/ads/googleads/v3/enums/extension_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,27 +41,39 @@ message AdGroupExtensionSetting {
     pattern: "customers/{customer}/adGroupExtensionSettings/{ad_group_extension_setting}"
   };
 
-  // The resource name of the ad group extension setting.
+  // Immutable. The resource name of the ad group extension setting.
   // AdGroupExtensionSetting resource names have the form:
   //
   // `customers/{customer_id}/adGroupExtensionSettings/{ad_group_id}~{extension_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupExtensionSetting"
+    }
+  ];
 
-  // The extension type of the ad group extension setting.
-  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2;
+  // Immutable. The extension type of the ad group extension setting.
+  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The resource name of the ad group. The linked extension feed items will
+  // Immutable. The resource name of the ad group. The linked extension feed items will
   // serve under this ad group.
   // AdGroup resource names have the form:
   //
   // `customers/{customer_id}/adGroups/{ad_group_id}`
-  google.protobuf.StringValue ad_group = 3;
+  google.protobuf.StringValue ad_group = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
   // The resource names of the extension feed items to serve under the ad group.
   // ExtensionFeedItem resource names have the form:
   //
   // `customers/{customer_id}/extensionFeedItems/{feed_item_id}`
-  repeated google.protobuf.StringValue extension_feed_items = 4;
+  repeated google.protobuf.StringValue extension_feed_items = 4 [(google.api.resource_reference) = {
+                                                                   type: "googleads.googleapis.com/ExtensionFeedItem"
+                                                                 }];
 
   // The device for which the extensions will serve. Optional.
   google.ads.googleads.v3.enums.ExtensionSettingDeviceEnum.ExtensionSettingDevice device = 5;
diff --git a/google/ads/googleads/v3/resources/ad_group_feed.proto b/google/ads/googleads/v3/resources/ad_group_feed.proto
index d2770e82..f3ed3fca 100644
--- a/google/ads/googleads/v3/resources/ad_group_feed.proto
+++ b/google/ads/googleads/v3/resources/ad_group_feed.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/matching_function.proto";
 import "google/ads/googleads/v3/enums/feed_link_status.proto";
 import "google/ads/googleads/v3/enums/placeholder_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,17 +42,32 @@ message AdGroupFeed {
     pattern: "customers/{customer}/adGroupFeeds/{ad_group_feed}"
   };
 
-  // The resource name of the ad group feed.
+  // Immutable. The resource name of the ad group feed.
   // Ad group feed resource names have the form:
   //
   // `customers/{customer_id}/adGroupFeeds/{ad_group_id}~{feed_id}
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupFeed"
+    }
+  ];
 
-  // The feed being linked to the ad group.
-  google.protobuf.StringValue feed = 2;
+  // Immutable. The feed being linked to the ad group.
+  google.protobuf.StringValue feed = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // The ad group being linked to the feed.
-  google.protobuf.StringValue ad_group = 3;
+  // Immutable. The ad group being linked to the feed.
+  google.protobuf.StringValue ad_group = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
   // Indicates which placeholder types the feed may populate under the connected
   // ad group. Required.
@@ -62,7 +78,7 @@ message AdGroupFeed {
   // Required.
   google.ads.googleads.v3.common.MatchingFunction matching_function = 5;
 
-  // Status of the ad group feed.
+  // Output only. Status of the ad group feed.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 6;
+  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_label.proto b/google/ads/googleads/v3/resources/ad_group_label.proto
index 36661ecf..e6213c35 100644
--- a/google/ads/googleads/v3/resources/ad_group_label.proto
+++ b/google/ads/googleads/v3/resources/ad_group_label.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,14 +39,29 @@ message AdGroupLabel {
     pattern: "customers/{customer}/adGroupLabels/{ad_group_label}"
   };
 
-  // The resource name of the ad group label.
+  // Immutable. The resource name of the ad group label.
   // Ad group label resource names have the form:
   // `customers/{customer_id}/adGroupLabels/{ad_group_id}~{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupLabel"
+    }
+  ];
 
-  // The ad group to which the label is attached.
-  google.protobuf.StringValue ad_group = 2;
+  // Immutable. The ad group to which the label is attached.
+  google.protobuf.StringValue ad_group = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // The label assigned to the ad group.
-  google.protobuf.StringValue label = 3;
+  // Immutable. The label assigned to the ad group.
+  google.protobuf.StringValue label = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Label"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/ad_group_simulation.proto b/google/ads/googleads/v3/resources/ad_group_simulation.proto
index 1596afab..d0503799 100644
--- a/google/ads/googleads/v3/resources/ad_group_simulation.proto
+++ b/google/ads/googleads/v3/resources/ad_group_simulation.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/simulation.proto";
 import "google/ads/googleads/v3/enums/simulation_modification_method.proto";
 import "google/ads/googleads/v3/enums/simulation_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -52,36 +53,41 @@ message AdGroupSimulation {
     pattern: "customers/{customer}/adGroupSimulations/{ad_group_simulation}"
   };
 
-  // The resource name of the ad group simulation.
+  // Output only. The resource name of the ad group simulation.
   // Ad group simulation resource names have the form:
   //
   // `customers/{customer_id}/adGroupSimulations/{ad_group_id}~{type}~{modification_method}~{start_date}~{end_date}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupSimulation"
+    }
+  ];
 
-  // Ad group id of the simulation.
-  google.protobuf.Int64Value ad_group_id = 2;
+  // Output only. Ad group id of the simulation.
+  google.protobuf.Int64Value ad_group_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The field that the simulation modifies.
-  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 3;
+  // Output only. The field that the simulation modifies.
+  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // How the simulation modifies the field.
-  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 4;
+  // Output only. How the simulation modifies the field.
+  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // First day on which the simulation is based, in YYYY-MM-DD format.
-  google.protobuf.StringValue start_date = 5;
+  // Output only. First day on which the simulation is based, in YYYY-MM-DD format.
+  google.protobuf.StringValue start_date = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Last day on which the simulation is based, in YYYY-MM-DD format
-  google.protobuf.StringValue end_date = 6;
+  // Output only. Last day on which the simulation is based, in YYYY-MM-DD format
+  google.protobuf.StringValue end_date = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // List of simulation points.
   oneof point_list {
-    // Simulation points if the simulation type is CPC_BID.
-    google.ads.googleads.v3.common.CpcBidSimulationPointList cpc_bid_point_list = 8;
+    // Output only. Simulation points if the simulation type is CPC_BID.
+    google.ads.googleads.v3.common.CpcBidSimulationPointList cpc_bid_point_list = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Simulation points if the simulation type is CPV_BID.
-    google.ads.googleads.v3.common.CpvBidSimulationPointList cpv_bid_point_list = 10;
+    // Output only. Simulation points if the simulation type is CPV_BID.
+    google.ads.googleads.v3.common.CpvBidSimulationPointList cpv_bid_point_list = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Simulation points if the simulation type is TARGET_CPA.
-    google.ads.googleads.v3.common.TargetCpaSimulationPointList target_cpa_point_list = 9;
+    // Output only. Simulation points if the simulation type is TARGET_CPA.
+    google.ads.googleads.v3.common.TargetCpaSimulationPointList target_cpa_point_list = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/ad_parameter.proto b/google/ads/googleads/v3/resources/ad_parameter.proto
index 3763578a..d19383e3 100644
--- a/google/ads/googleads/v3/resources/ad_parameter.proto
+++ b/google/ads/googleads/v3/resources/ad_parameter.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,17 +44,27 @@ message AdParameter {
     pattern: "customers/{customer}/adParameters/{ad_parameter}"
   };
 
-  // The resource name of the ad parameter.
+  // Immutable. The resource name of the ad parameter.
   // Ad parameter resource names have the form:
   //
   // `customers/{customer_id}/adParameters/{ad_group_id}~{criterion_id}~{parameter_index}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdParameter"
+    }
+  ];
 
-  // The ad group criterion that this ad parameter belongs to.
-  google.protobuf.StringValue ad_group_criterion = 2;
+  // Immutable. The ad group criterion that this ad parameter belongs to.
+  google.protobuf.StringValue ad_group_criterion = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterion"
+    }
+  ];
 
-  // The unique index of this ad parameter. Must be either 1 or 2.
-  google.protobuf.Int64Value parameter_index = 3;
+  // Immutable. The unique index of this ad parameter. Must be either 1 or 2.
+  google.protobuf.Int64Value parameter_index = 3 [(google.api.field_behavior) = IMMUTABLE];
 
   // Numeric value to insert into the ad text. The following restrictions
   //  apply:
diff --git a/google/ads/googleads/v3/resources/ad_schedule_view.proto b/google/ads/googleads/v3/resources/ad_schedule_view.proto
index 4dd9378f..3e667ac0 100644
--- a/google/ads/googleads/v3/resources/ad_schedule_view.proto
+++ b/google/ads/googleads/v3/resources/ad_schedule_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -38,9 +39,14 @@ message AdScheduleView {
     pattern: "customers/{customer}/adScheduleViews/{ad_schedule_view}"
   };
 
-  // The resource name of the ad schedule view.
+  // Output only. The resource name of the ad schedule view.
   // AdSchedule view resource names have the form:
   //
   // `customers/{customer_id}/adScheduleViews/{campaign_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdScheduleView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/age_range_view.proto b/google/ads/googleads/v3/resources/age_range_view.proto
index 6175f550..83b9450f 100644
--- a/google/ads/googleads/v3/resources/age_range_view.proto
+++ b/google/ads/googleads/v3/resources/age_range_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message AgeRangeView {
     pattern: "customers/{customer}/ageRangeViews/{age_range_view}"
   };
 
-  // The resource name of the age range view.
+  // Output only. The resource name of the age range view.
   // Age range view resource names have the form:
   //
   // `customers/{customer_id}/ageRangeViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AgeRangeView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/asset.proto b/google/ads/googleads/v3/resources/asset.proto
index a9aa6d5d..556d6328 100644
--- a/google/ads/googleads/v3/resources/asset.proto
+++ b/google/ads/googleads/v3/resources/asset.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/asset_types.proto";
 import "google/ads/googleads/v3/enums/asset_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,33 +42,38 @@ message Asset {
     pattern: "customers/{customer}/assets/{asset}"
   };
 
-  // The resource name of the asset.
+  // Immutable. The resource name of the asset.
   // Asset resource names have the form:
   //
   // `customers/{customer_id}/assets/{asset_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Asset"
+    }
+  ];
 
-  // The ID of the asset.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the asset.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Optional name of the asset.
-  google.protobuf.StringValue name = 3;
+  // Immutable. Optional name of the asset.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Type of the asset.
-  google.ads.googleads.v3.enums.AssetTypeEnum.AssetType type = 4;
+  // Output only. Type of the asset.
+  google.ads.googleads.v3.enums.AssetTypeEnum.AssetType type = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The specific type of the asset.
   oneof asset_data {
-    // A YouTube video asset.
-    google.ads.googleads.v3.common.YoutubeVideoAsset youtube_video_asset = 5;
+    // Immutable. A YouTube video asset.
+    google.ads.googleads.v3.common.YoutubeVideoAsset youtube_video_asset = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-    // A media bundle asset.
-    google.ads.googleads.v3.common.MediaBundleAsset media_bundle_asset = 6;
+    // Immutable. A media bundle asset.
+    google.ads.googleads.v3.common.MediaBundleAsset media_bundle_asset = 6 [(google.api.field_behavior) = IMMUTABLE];
 
-    // An image asset.
-    google.ads.googleads.v3.common.ImageAsset image_asset = 7;
+    // Output only. An image asset.
+    google.ads.googleads.v3.common.ImageAsset image_asset = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // A text asset.
-    google.ads.googleads.v3.common.TextAsset text_asset = 8;
+    // Output only. A text asset.
+    google.ads.googleads.v3.common.TextAsset text_asset = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/bidding_strategy.proto b/google/ads/googleads/v3/resources/bidding_strategy.proto
index 74ed29f9..5a45e755 100644
--- a/google/ads/googleads/v3/resources/bidding_strategy.proto
+++ b/google/ads/googleads/v3/resources/bidding_strategy.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/bidding.proto";
 import "google/ads/googleads/v3/enums/bidding_strategy_status.proto";
 import "google/ads/googleads/v3/enums/bidding_strategy_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,14 +42,19 @@ message BiddingStrategy {
     pattern: "customers/{customer}/biddingStrategies/{bidding_strategy}"
   };
 
-  // The resource name of the bidding strategy.
+  // Immutable. The resource name of the bidding strategy.
   // Bidding strategy resource names have the form:
   //
   // `customers/{customer_id}/biddingStrategies/{bidding_strategy_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/BiddingStrategy"
+    }
+  ];
 
-  // The ID of the bidding strategy.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the bidding strategy.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the bidding strategy.
   // All bidding strategies within an account must be named distinctly.
@@ -57,26 +63,26 @@ message BiddingStrategy {
   // in UTF-8 bytes, (trimmed).
   google.protobuf.StringValue name = 4;
 
-  // The status of the bidding strategy.
+  // Output only. The status of the bidding strategy.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.BiddingStrategyStatusEnum.BiddingStrategyStatus status = 15;
+  google.ads.googleads.v3.enums.BiddingStrategyStatusEnum.BiddingStrategyStatus status = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of the bidding strategy.
+  // Output only. The type of the bidding strategy.
   // Create a bidding strategy by setting the bidding scheme.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.BiddingStrategyTypeEnum.BiddingStrategyType type = 5;
+  google.ads.googleads.v3.enums.BiddingStrategyTypeEnum.BiddingStrategyType type = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The number of campaigns attached to this bidding strategy.
+  // Output only. The number of campaigns attached to this bidding strategy.
   //
   // This field is read-only.
-  google.protobuf.Int64Value campaign_count = 13;
+  google.protobuf.Int64Value campaign_count = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The number of non-removed campaigns attached to this bidding strategy.
+  // Output only. The number of non-removed campaigns attached to this bidding strategy.
   //
   // This field is read-only.
-  google.protobuf.Int64Value non_removed_campaign_count = 14;
+  google.protobuf.Int64Value non_removed_campaign_count = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The bidding scheme.
   //
diff --git a/google/ads/googleads/v3/resources/billing_setup.proto b/google/ads/googleads/v3/resources/billing_setup.proto
index 0a794c6d..f37f5917 100644
--- a/google/ads/googleads/v3/resources/billing_setup.proto
+++ b/google/ads/googleads/v3/resources/billing_setup.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/billing_setup_status.proto";
 import "google/ads/googleads/v3/enums/time_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,47 +44,52 @@ message BillingSetup {
 
   // Container of payments account information for this billing.
   message PaymentsAccountInfo {
-    // A 16 digit id used to identify the payments account associated with the
+    // Output only. A 16 digit id used to identify the payments account associated with the
     // billing setup.
     //
     // This must be passed as a string with dashes, e.g. "1234-5678-9012-3456".
-    google.protobuf.StringValue payments_account_id = 1;
+    google.protobuf.StringValue payments_account_id = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The name of the payments account associated with the billing setup.
+    // Immutable. The name of the payments account associated with the billing setup.
     //
     // This enables the user to specify a meaningful name for a payments account
     // to aid in reconciling monthly invoices.
     //
     // This name will be printed in the monthly invoices.
-    google.protobuf.StringValue payments_account_name = 2;
+    google.protobuf.StringValue payments_account_name = 2 [(google.api.field_behavior) = IMMUTABLE];
 
-    // A 12 digit id used to identify the payments profile associated with the
+    // Immutable. A 12 digit id used to identify the payments profile associated with the
     // billing setup.
     //
     // This must be passed in as a string with dashes, e.g. "1234-5678-9012".
-    google.protobuf.StringValue payments_profile_id = 3;
+    google.protobuf.StringValue payments_profile_id = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The name of the payments profile associated with the billing setup.
-    google.protobuf.StringValue payments_profile_name = 4;
+    // Output only. The name of the payments profile associated with the billing setup.
+    google.protobuf.StringValue payments_profile_name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // A secondary payments profile id present in uncommon situations, e.g.
+    // Output only. A secondary payments profile id present in uncommon situations, e.g.
     // when a sequential liability agreement has been arranged.
-    google.protobuf.StringValue secondary_payments_profile_id = 5;
+    google.protobuf.StringValue secondary_payments_profile_id = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The resource name of the billing setup.
+  // Immutable. The resource name of the billing setup.
   // BillingSetup resource names have the form:
   //
   // `customers/{customer_id}/billingSetups/{billing_setup_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/BillingSetup"
+    }
+  ];
 
-  // The ID of the billing setup.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the billing setup.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The status of the billing setup.
-  google.ads.googleads.v3.enums.BillingSetupStatusEnum.BillingSetupStatus status = 3;
+  // Output only. The status of the billing setup.
+  google.ads.googleads.v3.enums.BillingSetupStatusEnum.BillingSetupStatus status = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the payments account associated with this billing
+  // Immutable. The resource name of the payments account associated with this billing
   // setup. Payments resource names have the form:
   //
   // `customers/{customer_id}/paymentsAccounts/{payments_account_id}`
@@ -91,14 +97,19 @@ message BillingSetup {
   // account (and then payments_account_info should not be set).
   // When getting a billing setup, this and payments_account_info will be
   // populated.
-  google.protobuf.StringValue payments_account = 11;
+  google.protobuf.StringValue payments_account = 11 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/PaymentsAccount"
+    }
+  ];
 
-  // The payments account information associated with this billing setup.
+  // Immutable. The payments account information associated with this billing setup.
   // When setting up billing, this is used to signup with a new payments account
   // (and then payments_account should not be set).
   // When getting a billing setup, this and payments_account will be
   // populated.
-  PaymentsAccountInfo payments_account_info = 12;
+  PaymentsAccountInfo payments_account_info = 12 [(google.api.field_behavior) = IMMUTABLE];
 
   // When creating a new billing setup, this is when the setup should take
   // effect. NOW is the only acceptable start time if the customer doesn't have
@@ -108,21 +119,21 @@ message BillingSetup {
   // However, if the setup was approved (see status) after the requested start
   // time, then this is the approval time.
   oneof start_time {
-    // The start date time in yyyy-MM-dd or yyyy-MM-dd HH:mm:ss format. Only a
+    // Immutable. The start date time in yyyy-MM-dd or yyyy-MM-dd HH:mm:ss format. Only a
     // future time is allowed.
-    google.protobuf.StringValue start_date_time = 9;
+    google.protobuf.StringValue start_date_time = 9 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The start time as a type. Only NOW is allowed.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType start_time_type = 10;
+    // Immutable. The start time as a type. Only NOW is allowed.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType start_time_type = 10 [(google.api.field_behavior) = IMMUTABLE];
   }
 
   // When the billing setup ends / ended. This is either FOREVER or the start
   // time of the next scheduled billing setup.
   oneof end_time {
-    // The end date time in yyyy-MM-dd or yyyy-MM-dd HH:mm:ss format.
-    google.protobuf.StringValue end_date_time = 13;
+    // Output only. The end date time in yyyy-MM-dd or yyyy-MM-dd HH:mm:ss format.
+    google.protobuf.StringValue end_date_time = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The end time as a type.  The only possible value is FOREVER.
-    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType end_time_type = 14;
+    // Output only. The end time as a type.  The only possible value is FOREVER.
+    google.ads.googleads.v3.enums.TimeTypeEnum.TimeType end_time_type = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/campaign.proto b/google/ads/googleads/v3/resources/campaign.proto
index 1b3cd476..edc2ca64 100644
--- a/google/ads/googleads/v3/resources/campaign.proto
+++ b/google/ads/googleads/v3/resources/campaign.proto
@@ -36,6 +36,7 @@ import "google/ads/googleads/v3/enums/payment_mode.proto";
 import "google/ads/googleads/v3/enums/positive_geo_target_type.proto";
 import "google/ads/googleads/v3/enums/vanity_pharma_display_url_mode.proto";
 import "google/ads/googleads/v3/enums/vanity_pharma_text.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -78,8 +79,8 @@ message Campaign {
 
   // Campaign-level settings for hotel ads.
   message HotelSettingInfo {
-    // The linked Hotel Center account.
-    google.protobuf.Int64Value hotel_center_id = 1;
+    // Immutable. The linked Hotel Center account.
+    google.protobuf.Int64Value hotel_center_id = 1 [(google.api.field_behavior) = IMMUTABLE];
   }
 
   // Campaign-level settings for App Campaigns.
@@ -88,11 +89,20 @@ message Campaign {
     // should optimize towards.
     google.ads.googleads.v3.enums.AppCampaignBiddingStrategyGoalTypeEnum.AppCampaignBiddingStrategyGoalType bidding_strategy_goal_type = 1;
 
-    // A string that uniquely identifies a mobile application.
-    google.protobuf.StringValue app_id = 2;
+    // Immutable. A string that uniquely identifies a mobile application.
+    google.protobuf.StringValue app_id = 2 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The application store that distributes this specific app.
-    google.ads.googleads.v3.enums.AppCampaignAppStoreEnum.AppCampaignAppStore app_store = 3;
+    // Immutable. The application store that distributes this specific app.
+    google.ads.googleads.v3.enums.AppCampaignAppStoreEnum.AppCampaignAppStore app_store = 3 [(google.api.field_behavior) = IMMUTABLE];
+  }
+
+  // Selective optimization setting for this campaign, which includes a set of
+  // conversion actions to optimize this campaign towards.
+  message SelectiveOptimization {
+    // The selected set of conversion actions for optimizing this campaign.
+    repeated google.protobuf.StringValue conversion_actions = 1 [(google.api.resource_reference) = {
+                                                                   type: "googleads.googleapis.com/ConversionAction"
+                                                                 }];
   }
 
   // The setting for controlling Dynamic Search Ads (DSA).
@@ -107,24 +117,39 @@ message Campaign {
     // Whether the campaign uses advertiser supplied URLs exclusively.
     google.protobuf.BoolValue use_supplied_urls_only = 3;
 
-    // The list of page feeds associated with the campaign.
-    repeated google.protobuf.StringValue feeds = 5;
+    // Output only. The list of page feeds associated with the campaign.
+    repeated google.protobuf.StringValue feeds = 5 [
+      (google.api.field_behavior) = OUTPUT_ONLY,
+      (google.api.resource_reference) = {
+        type: "googleads.googleapis.com/Feed"
+      }
+    ];
+  }
+
+  // Describes how unbranded pharma ads will be displayed.
+  message VanityPharma {
+    // The display mode for vanity pharma URLs.
+    google.ads.googleads.v3.enums.VanityPharmaDisplayUrlModeEnum.VanityPharmaDisplayUrlMode vanity_pharma_display_url_mode = 1;
+
+    // The text that will be displayed in display URL of the text ad when
+    // website description is the selected display mode for vanity pharma URLs.
+    google.ads.googleads.v3.enums.VanityPharmaTextEnum.VanityPharmaText vanity_pharma_text = 2;
   }
 
   // The setting for Shopping campaigns. Defines the universe of products that
   // can be advertised by the campaign, and how this campaign interacts with
   // other Shopping campaigns.
   message ShoppingSetting {
-    // ID of the Merchant Center account.
+    // Immutable. ID of the Merchant Center account.
     // This field is required for create operations. This field is immutable for
     // Shopping campaigns.
-    google.protobuf.Int64Value merchant_id = 1;
+    google.protobuf.Int64Value merchant_id = 1 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Sales country of products to include in the campaign.
+    // Immutable. Sales country of products to include in the campaign.
     // This field is required for Shopping campaigns. This field is immutable.
     // This field is optional for non-Shopping campaigns, but it must be equal
     // to 'ZZ' if set.
-    google.protobuf.StringValue sales_country = 2;
+    google.protobuf.StringValue sales_country = 2 [(google.api.field_behavior) = IMMUTABLE];
 
     // Priority of the campaign. Campaigns with numerically higher priorities
     // take precedence over those with lower priorities.
@@ -138,21 +163,10 @@ message Campaign {
     google.protobuf.BoolValue enable_local = 4;
   }
 
-  // Describes how unbranded pharma ads will be displayed.
-  message VanityPharma {
-    // The display mode for vanity pharma URLs.
-    google.ads.googleads.v3.enums.VanityPharmaDisplayUrlModeEnum.VanityPharmaDisplayUrlMode vanity_pharma_display_url_mode = 1;
-
-    // The text that will be displayed in display URL of the text ad when
-    // website description is the selected display mode for vanity pharma URLs.
-    google.ads.googleads.v3.enums.VanityPharmaTextEnum.VanityPharmaText vanity_pharma_text = 2;
-  }
-
-  // Selective optimization setting for this campaign, which includes a set of
-  // conversion actions to optimize this campaign towards.
-  message SelectiveOptimization {
-    // The selected set of conversion actions for optimizing this campaign.
-    repeated google.protobuf.StringValue conversion_actions = 1;
+  // Campaign-level settings for tracking information.
+  message TrackingSetting {
+    // Output only. The url used for dynamic tracking.
+    google.protobuf.StringValue tracking_url = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // Represents a collection of settings related to ads geotargeting.
@@ -164,20 +178,19 @@ message Campaign {
     google.ads.googleads.v3.enums.NegativeGeoTargetTypeEnum.NegativeGeoTargetType negative_geo_target_type = 2;
   }
 
-  // Campaign-level settings for tracking information.
-  message TrackingSetting {
-    // The url used for dynamic tracking.
-    google.protobuf.StringValue tracking_url = 1;
-  }
-
-  // The resource name of the campaign.
+  // Immutable. The resource name of the campaign.
   // Campaign resource names have the form:
   //
   // `customers/{customer_id}/campaigns/{campaign_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The ID of the campaign.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the campaign.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the campaign.
   //
@@ -193,13 +206,13 @@ message Campaign {
   // When a new campaign is added, the status defaults to ENABLED.
   google.ads.googleads.v3.enums.CampaignStatusEnum.CampaignStatus status = 5;
 
-  // The ad serving status of the campaign.
-  google.ads.googleads.v3.enums.CampaignServingStatusEnum.CampaignServingStatus serving_status = 21;
+  // Output only. The ad serving status of the campaign.
+  google.ads.googleads.v3.enums.CampaignServingStatusEnum.CampaignServingStatus serving_status = 21 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The ad serving optimization status of the campaign.
   google.ads.googleads.v3.enums.AdServingOptimizationStatusEnum.AdServingOptimizationStatus ad_serving_optimization_status = 8;
 
-  // The primary serving target for ads within the campaign.
+  // Immutable. The primary serving target for ads within the campaign.
   // The targeting options can be refined in `network_settings`.
   //
   // This field is required and should not be empty when creating new
@@ -207,14 +220,14 @@ message Campaign {
   //
   // Can be set only when creating campaigns.
   // After the campaign is created, the field can not be changed.
-  google.ads.googleads.v3.enums.AdvertisingChannelTypeEnum.AdvertisingChannelType advertising_channel_type = 9;
+  google.ads.googleads.v3.enums.AdvertisingChannelTypeEnum.AdvertisingChannelType advertising_channel_type = 9 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Optional refinement to `advertising_channel_type`.
+  // Immutable. Optional refinement to `advertising_channel_type`.
   // Must be a valid sub-type of the parent channel type.
   //
   // Can be set only when creating campaigns.
   // After campaign is created, the field can not be changed.
-  google.ads.googleads.v3.enums.AdvertisingChannelSubTypeEnum.AdvertisingChannelSubType advertising_channel_sub_type = 10;
+  google.ads.googleads.v3.enums.AdvertisingChannelSubTypeEnum.AdvertisingChannelSubType advertising_channel_sub_type = 10 [(google.api.field_behavior) = IMMUTABLE];
 
   // The URL template for constructing a tracking URL.
   google.protobuf.StringValue tracking_url_template = 11;
@@ -230,8 +243,8 @@ message Campaign {
   // The network settings for the campaign.
   NetworkSettings network_settings = 14;
 
-  // The hotel setting for the campaign.
-  HotelSettingInfo hotel_setting = 32;
+  // Immutable. The hotel setting for the campaign.
+  HotelSettingInfo hotel_setting = 32 [(google.api.field_behavior) = IMMUTABLE];
 
   // The setting for controlling Dynamic Search Ads (DSA).
   DynamicSearchAdsSetting dynamic_search_ads_setting = 33;
@@ -248,29 +261,41 @@ message Campaign {
   // The setting related to App Campaign.
   AppCampaignSetting app_campaign_setting = 51;
 
-  // The resource names of labels attached to this campaign.
-  repeated google.protobuf.StringValue labels = 53;
+  // Output only. The resource names of labels attached to this campaign.
+  repeated google.protobuf.StringValue labels = 53 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignLabel"
+    }
+  ];
 
-  // The type of campaign: normal, draft, or experiment.
-  google.ads.googleads.v3.enums.CampaignExperimentTypeEnum.CampaignExperimentType experiment_type = 17;
+  // Output only. The type of campaign: normal, draft, or experiment.
+  google.ads.googleads.v3.enums.CampaignExperimentTypeEnum.CampaignExperimentType experiment_type = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the base campaign of a draft or experiment campaign.
+  // Output only. The resource name of the base campaign of a draft or experiment campaign.
   // For base campaigns, this is equal to `resource_name`.
   //
   // This field is read-only.
-  google.protobuf.StringValue base_campaign = 28;
+  google.protobuf.StringValue base_campaign = 28 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
   // The budget of the campaign.
-  google.protobuf.StringValue campaign_budget = 6;
+  google.protobuf.StringValue campaign_budget = 6 [(google.api.resource_reference) = {
+                                                     type: "googleads.googleapis.com/CampaignBudget"
+                                                   }];
 
-  // The type of bidding strategy.
+  // Output only. The type of bidding strategy.
   //
   // A bidding strategy can be created by setting either the bidding scheme to
   // create a standard bidding strategy or the `bidding_strategy` field to
   // create a portfolio bidding strategy.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.BiddingStrategyTypeEnum.BiddingStrategyType bidding_strategy_type = 22;
+  google.ads.googleads.v3.enums.BiddingStrategyTypeEnum.BiddingStrategyType bidding_strategy_type = 22 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The date when campaign started.
   //
@@ -289,8 +314,8 @@ message Campaign {
   // A list that limits how often each user will see this campaign's ads.
   repeated google.ads.googleads.v3.common.FrequencyCapEntry frequency_caps = 40;
 
-  // 3-Tier Brand Safety setting for the campaign.
-  google.ads.googleads.v3.enums.BrandSafetySuitabilityEnum.BrandSafetySuitability video_brand_safety_suitability = 42;
+  // Output only. 3-Tier Brand Safety setting for the campaign.
+  google.ads.googleads.v3.enums.BrandSafetySuitabilityEnum.BrandSafetySuitability video_brand_safety_suitability = 42 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Describes how unbranded pharma ads will be displayed.
   VanityPharma vanity_pharma = 44;
@@ -299,8 +324,8 @@ message Campaign {
   // conversion actions to optimize this campaign towards.
   SelectiveOptimization selective_optimization = 45;
 
-  // Campaign-level settings for tracking information.
-  TrackingSetting tracking_setting = 46;
+  // Output only. Campaign-level settings for tracking information.
+  TrackingSetting tracking_setting = 46 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Payment mode for the campaign.
   google.ads.googleads.v3.enums.PaymentModeEnum.PaymentMode payment_mode = 52;
@@ -311,7 +336,9 @@ message Campaign {
   // standard, that is embedded into the campaign.
   oneof campaign_bidding_strategy {
     // Portfolio bidding strategy used by campaign.
-    google.protobuf.StringValue bidding_strategy = 23;
+    google.protobuf.StringValue bidding_strategy = 23 [(google.api.resource_reference) = {
+                                                         type: "googleads.googleapis.com/BiddingStrategy"
+                                                       }];
 
     // Commission is an automatic bidding strategy in which the advertiser pays
     // a certain portion of the conversion value.
@@ -326,8 +353,8 @@ message Campaign {
     // impressions.
     google.ads.googleads.v3.common.ManualCpm manual_cpm = 25;
 
-    // A bidding strategy that pays a configurable amount per video view.
-    google.ads.googleads.v3.common.ManualCpv manual_cpv = 37;
+    // Output only. A bidding strategy that pays a configurable amount per video view.
+    google.ads.googleads.v3.common.ManualCpv manual_cpv = 37 [(google.api.field_behavior) = OUTPUT_ONLY];
 
     // Standard Maximize Conversions bidding strategy that automatically
     // maximizes number of conversions given a daily budget.
diff --git a/google/ads/googleads/v3/resources/campaign_audience_view.proto b/google/ads/googleads/v3/resources/campaign_audience_view.proto
index 3cd43012..a6896869 100644
--- a/google/ads/googleads/v3/resources/campaign_audience_view.proto
+++ b/google/ads/googleads/v3/resources/campaign_audience_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -41,9 +42,14 @@ message CampaignAudienceView {
     pattern: "customers/{customer}/campaignAudienceViews/{campaign_audience_view}"
   };
 
-  // The resource name of the campaign audience view.
+  // Output only. The resource name of the campaign audience view.
   // Campaign audience view resource names have the form:
   //
   // `customers/{customer_id}/campaignAudienceViews/{campaign_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignAudienceView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/campaign_bid_modifier.proto b/google/ads/googleads/v3/resources/campaign_bid_modifier.proto
index 6c2d82f6..0a5ce82f 100644
--- a/google/ads/googleads/v3/resources/campaign_bid_modifier.proto
+++ b/google/ads/googleads/v3/resources/campaign_bid_modifier.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/criteria.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,26 +40,36 @@ message CampaignBidModifier {
     pattern: "customers/{customer}/campaignBidModifiers/{campaign_bid_modifier}"
   };
 
-  // The resource name of the campaign bid modifier.
+  // Immutable. The resource name of the campaign bid modifier.
   // Campaign bid modifier resource names have the form:
   //
   // `customers/{customer_id}/campaignBidModifiers/{campaign_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignBidModifier"
+    }
+  ];
 
-  // The campaign to which this criterion belongs.
-  google.protobuf.StringValue campaign = 2;
+  // Output only. The campaign to which this criterion belongs.
+  google.protobuf.StringValue campaign = 2 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The ID of the criterion to bid modify.
+  // Output only. The ID of the criterion to bid modify.
   //
   // This field is ignored for mutates.
-  google.protobuf.Int64Value criterion_id = 3;
+  google.protobuf.Int64Value criterion_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The modifier for the bid when the criterion matches.
   google.protobuf.DoubleValue bid_modifier = 4;
 
   // The criterion of this campaign bid modifier.
   oneof criterion {
-    // Criterion for interaction type. Only supported for search campaigns.
-    google.ads.googleads.v3.common.InteractionTypeInfo interaction_type = 5;
+    // Immutable. Criterion for interaction type. Only supported for search campaigns.
+    google.ads.googleads.v3.common.InteractionTypeInfo interaction_type = 5 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/campaign_budget.proto b/google/ads/googleads/v3/resources/campaign_budget.proto
index 4d8f11db..46b1a7a3 100644
--- a/google/ads/googleads/v3/resources/campaign_budget.proto
+++ b/google/ads/googleads/v3/resources/campaign_budget.proto
@@ -20,6 +20,7 @@ import "google/ads/googleads/v3/enums/budget_delivery_method.proto";
 import "google/ads/googleads/v3/enums/budget_period.proto";
 import "google/ads/googleads/v3/enums/budget_status.proto";
 import "google/ads/googleads/v3/enums/budget_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -42,19 +43,24 @@ message CampaignBudget {
     pattern: "customers/{customer}/campaignBudgets/{campaign_budget}"
   };
 
-  // The resource name of the campaign budget.
+  // Immutable. The resource name of the campaign budget.
   // Campaign budget resource names have the form:
   //
   // `customers/{customer_id}/campaignBudgets/{budget_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignBudget"
+    }
+  ];
 
-  // The ID of the campaign budget.
+  // Output only. The ID of the campaign budget.
   //
   // A campaign budget is created using the CampaignBudgetService create
   // operation and is assigned a budget ID. A budget ID can be shared across
   // different campaigns; the system will then allocate the campaign budget
   // among different campaigns to get optimum results.
-  google.protobuf.Int64Value id = 3;
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the campaign budget.
   //
@@ -77,8 +83,8 @@ message CampaignBudget {
   // currency unit.
   google.protobuf.Int64Value total_amount_micros = 10;
 
-  // The status of this campaign budget. This field is read-only.
-  google.ads.googleads.v3.enums.BudgetStatusEnum.BudgetStatus status = 6;
+  // Output only. The status of this campaign budget. This field is read-only.
+  google.ads.googleads.v3.enums.BudgetStatusEnum.BudgetStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The delivery method that determines the rate at which the campaign budget
   // is spent.
@@ -103,49 +109,49 @@ message CampaignBudget {
   // A shared campaign budget can never become non-shared.
   google.protobuf.BoolValue explicitly_shared = 8;
 
-  // The number of campaigns actively using the budget.
+  // Output only. The number of campaigns actively using the budget.
   //
   // This field is read-only.
-  google.protobuf.Int64Value reference_count = 9;
+  google.protobuf.Int64Value reference_count = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Indicates whether there is a recommended budget for this campaign budget.
+  // Output only. Indicates whether there is a recommended budget for this campaign budget.
   //
   // This field is read-only.
-  google.protobuf.BoolValue has_recommended_budget = 11;
+  google.protobuf.BoolValue has_recommended_budget = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The recommended budget amount. If no recommendation is available, this will
+  // Output only. The recommended budget amount. If no recommendation is available, this will
   // be set to the budget amount.
   // Amount is specified in micros, where one million is equivalent to one
   // currency unit.
   //
   // This field is read-only.
-  google.protobuf.Int64Value recommended_budget_amount_micros = 12;
+  google.protobuf.Int64Value recommended_budget_amount_micros = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Period over which to spend the budget. Defaults to DAILY if not specified.
-  google.ads.googleads.v3.enums.BudgetPeriodEnum.BudgetPeriod period = 13;
+  // Immutable. Period over which to spend the budget. Defaults to DAILY if not specified.
+  google.ads.googleads.v3.enums.BudgetPeriodEnum.BudgetPeriod period = 13 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The estimated change in weekly clicks if the recommended budget is applied.
+  // Output only. The estimated change in weekly clicks if the recommended budget is applied.
   //
   // This field is read-only.
-  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_clicks = 14;
+  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_clicks = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The estimated change in weekly cost in micros if the recommended budget is
+  // Output only. The estimated change in weekly cost in micros if the recommended budget is
   // applied. One million is equivalent to one currency unit.
   //
   // This field is read-only.
-  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_cost_micros = 15;
+  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_cost_micros = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The estimated change in weekly interactions if the recommended budget is
+  // Output only. The estimated change in weekly interactions if the recommended budget is
   // applied.
   //
   // This field is read-only.
-  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_interactions = 16;
+  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_interactions = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The estimated change in weekly views if the recommended budget is applied.
+  // Output only. The estimated change in weekly views if the recommended budget is applied.
   //
   // This field is read-only.
-  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_views = 17;
+  google.protobuf.Int64Value recommended_budget_estimated_change_weekly_views = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of the campaign budget.
-  google.ads.googleads.v3.enums.BudgetTypeEnum.BudgetType type = 18;
+  // Immutable. The type of the campaign budget.
+  google.ads.googleads.v3.enums.BudgetTypeEnum.BudgetType type = 18 [(google.api.field_behavior) = IMMUTABLE];
 }
diff --git a/google/ads/googleads/v3/resources/campaign_criterion.proto b/google/ads/googleads/v3/resources/campaign_criterion.proto
index 8a64a344..3a84f0b3 100644
--- a/google/ads/googleads/v3/resources/campaign_criterion.proto
+++ b/google/ads/googleads/v3/resources/campaign_criterion.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/criteria.proto";
 import "google/ads/googleads/v3/enums/campaign_criterion_status.proto";
 import "google/ads/googleads/v3/enums/criterion_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,30 +42,40 @@ message CampaignCriterion {
     pattern: "customers/{customer}/campaignCriteria/{campaign_criterion}"
   };
 
-  // The resource name of the campaign criterion.
+  // Immutable. The resource name of the campaign criterion.
   // Campaign criterion resource names have the form:
   //
   // `customers/{customer_id}/campaignCriteria/{campaign_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignCriterion"
+    }
+  ];
 
-  // The campaign to which the criterion belongs.
-  google.protobuf.StringValue campaign = 4;
+  // Immutable. The campaign to which the criterion belongs.
+  google.protobuf.StringValue campaign = 4 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The ID of the criterion.
+  // Output only. The ID of the criterion.
   //
   // This field is ignored during mutate.
-  google.protobuf.Int64Value criterion_id = 5;
+  google.protobuf.Int64Value criterion_id = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The modifier for the bids when the criterion matches. The modifier must be
   // in the range: 0.1 - 10.0. Most targetable criteria types support modifiers.
   // Use 0 to opt out of a Device type.
   google.protobuf.FloatValue bid_modifier = 14;
 
-  // Whether to target (`false`) or exclude (`true`) the criterion.
-  google.protobuf.BoolValue negative = 7;
+  // Immutable. Whether to target (`false`) or exclude (`true`) the criterion.
+  google.protobuf.BoolValue negative = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The type of the criterion.
-  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 6;
+  // Output only. The type of the criterion.
+  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The status of the criterion.
   google.ads.googleads.v3.enums.CampaignCriterionStatusEnum.CampaignCriterionStatus status = 35;
@@ -73,85 +84,85 @@ message CampaignCriterion {
   //
   // Exactly one must be set.
   oneof criterion {
-    // Keyword.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 8;
+    // Immutable. Keyword.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Placement.
-    google.ads.googleads.v3.common.PlacementInfo placement = 9;
+    // Immutable. Placement.
+    google.ads.googleads.v3.common.PlacementInfo placement = 9 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile app category.
-    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 10;
+    // Immutable. Mobile app category.
+    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 10 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile application.
-    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 11;
+    // Immutable. Mobile application.
+    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 11 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Location.
-    google.ads.googleads.v3.common.LocationInfo location = 12;
+    // Immutable. Location.
+    google.ads.googleads.v3.common.LocationInfo location = 12 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Device.
-    google.ads.googleads.v3.common.DeviceInfo device = 13;
+    // Immutable. Device.
+    google.ads.googleads.v3.common.DeviceInfo device = 13 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Ad Schedule.
-    google.ads.googleads.v3.common.AdScheduleInfo ad_schedule = 15;
+    // Immutable. Ad Schedule.
+    google.ads.googleads.v3.common.AdScheduleInfo ad_schedule = 15 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Age range.
-    google.ads.googleads.v3.common.AgeRangeInfo age_range = 16;
+    // Immutable. Age range.
+    google.ads.googleads.v3.common.AgeRangeInfo age_range = 16 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Gender.
-    google.ads.googleads.v3.common.GenderInfo gender = 17;
+    // Immutable. Gender.
+    google.ads.googleads.v3.common.GenderInfo gender = 17 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Income range.
-    google.ads.googleads.v3.common.IncomeRangeInfo income_range = 18;
+    // Immutable. Income range.
+    google.ads.googleads.v3.common.IncomeRangeInfo income_range = 18 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Parental status.
-    google.ads.googleads.v3.common.ParentalStatusInfo parental_status = 19;
+    // Immutable. Parental status.
+    google.ads.googleads.v3.common.ParentalStatusInfo parental_status = 19 [(google.api.field_behavior) = IMMUTABLE];
 
-    // User List.
-    google.ads.googleads.v3.common.UserListInfo user_list = 22;
+    // Immutable. User List.
+    google.ads.googleads.v3.common.UserListInfo user_list = 22 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Video.
-    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 20;
+    // Immutable. YouTube Video.
+    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 20 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Channel.
-    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 21;
+    // Immutable. YouTube Channel.
+    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 21 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Proximity.
-    google.ads.googleads.v3.common.ProximityInfo proximity = 23;
+    // Immutable. Proximity.
+    google.ads.googleads.v3.common.ProximityInfo proximity = 23 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Topic.
-    google.ads.googleads.v3.common.TopicInfo topic = 24;
+    // Immutable. Topic.
+    google.ads.googleads.v3.common.TopicInfo topic = 24 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Listing scope.
-    google.ads.googleads.v3.common.ListingScopeInfo listing_scope = 25;
+    // Immutable. Listing scope.
+    google.ads.googleads.v3.common.ListingScopeInfo listing_scope = 25 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Language.
-    google.ads.googleads.v3.common.LanguageInfo language = 26;
+    // Immutable. Language.
+    google.ads.googleads.v3.common.LanguageInfo language = 26 [(google.api.field_behavior) = IMMUTABLE];
 
-    // IpBlock.
-    google.ads.googleads.v3.common.IpBlockInfo ip_block = 27;
+    // Immutable. IpBlock.
+    google.ads.googleads.v3.common.IpBlockInfo ip_block = 27 [(google.api.field_behavior) = IMMUTABLE];
 
-    // ContentLabel.
-    google.ads.googleads.v3.common.ContentLabelInfo content_label = 28;
+    // Immutable. ContentLabel.
+    google.ads.googleads.v3.common.ContentLabelInfo content_label = 28 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Carrier.
-    google.ads.googleads.v3.common.CarrierInfo carrier = 29;
+    // Immutable. Carrier.
+    google.ads.googleads.v3.common.CarrierInfo carrier = 29 [(google.api.field_behavior) = IMMUTABLE];
 
-    // User Interest.
-    google.ads.googleads.v3.common.UserInterestInfo user_interest = 30;
+    // Immutable. User Interest.
+    google.ads.googleads.v3.common.UserInterestInfo user_interest = 30 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Webpage.
-    google.ads.googleads.v3.common.WebpageInfo webpage = 31;
+    // Immutable. Webpage.
+    google.ads.googleads.v3.common.WebpageInfo webpage = 31 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Operating system version.
-    google.ads.googleads.v3.common.OperatingSystemVersionInfo operating_system_version = 32;
+    // Immutable. Operating system version.
+    google.ads.googleads.v3.common.OperatingSystemVersionInfo operating_system_version = 32 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile Device.
-    google.ads.googleads.v3.common.MobileDeviceInfo mobile_device = 33;
+    // Immutable. Mobile Device.
+    google.ads.googleads.v3.common.MobileDeviceInfo mobile_device = 33 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Location Group
-    google.ads.googleads.v3.common.LocationGroupInfo location_group = 34;
+    // Immutable. Location Group
+    google.ads.googleads.v3.common.LocationGroupInfo location_group = 34 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Custom Affinity.
-    google.ads.googleads.v3.common.CustomAffinityInfo custom_affinity = 36;
+    // Immutable. Custom Affinity.
+    google.ads.googleads.v3.common.CustomAffinityInfo custom_affinity = 36 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/campaign_criterion_simulation.proto b/google/ads/googleads/v3/resources/campaign_criterion_simulation.proto
index e5ff3473..f57a3ba7 100644
--- a/google/ads/googleads/v3/resources/campaign_criterion_simulation.proto
+++ b/google/ads/googleads/v3/resources/campaign_criterion_simulation.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/simulation.proto";
 import "google/ads/googleads/v3/enums/simulation_modification_method.proto";
 import "google/ads/googleads/v3/enums/simulation_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -47,33 +48,38 @@ message CampaignCriterionSimulation {
     pattern: "customers/{customer}/campaignCriterionSimulations/{campaign_criterion_simulation}"
   };
 
-  // The resource name of the campaign criterion simulation.
+  // Output only. The resource name of the campaign criterion simulation.
   // Campaign criterion simulation resource names have the form:
   //
   // `customers/{customer_id}/campaignCriterionSimulations/{campaign_id}~{criterion_id}~{type}~{modification_method}~{start_date}~{end_date}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignCriterionSimulation"
+    }
+  ];
 
-  // Campaign ID of the simulation.
-  google.protobuf.Int64Value campaign_id = 2;
+  // Output only. Campaign ID of the simulation.
+  google.protobuf.Int64Value campaign_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Criterion ID of the simulation.
-  google.protobuf.Int64Value criterion_id = 3;
+  // Output only. Criterion ID of the simulation.
+  google.protobuf.Int64Value criterion_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The field that the simulation modifies.
-  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 4;
+  // Output only. The field that the simulation modifies.
+  google.ads.googleads.v3.enums.SimulationTypeEnum.SimulationType type = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // How the simulation modifies the field.
-  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 5;
+  // Output only. How the simulation modifies the field.
+  google.ads.googleads.v3.enums.SimulationModificationMethodEnum.SimulationModificationMethod modification_method = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // First day on which the simulation is based, in YYYY-MM-DD format.
-  google.protobuf.StringValue start_date = 6;
+  // Output only. First day on which the simulation is based, in YYYY-MM-DD format.
+  google.protobuf.StringValue start_date = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Last day on which the simulation is based, in YYYY-MM-DD format.
-  google.protobuf.StringValue end_date = 7;
+  // Output only. Last day on which the simulation is based, in YYYY-MM-DD format.
+  google.protobuf.StringValue end_date = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // List of simulation points.
   oneof point_list {
-    // Simulation points if the simulation type is BID_MODIFIER.
-    google.ads.googleads.v3.common.BidModifierSimulationPointList bid_modifier_point_list = 8;
+    // Output only. Simulation points if the simulation type is BID_MODIFIER.
+    google.ads.googleads.v3.common.BidModifierSimulationPointList bid_modifier_point_list = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/campaign_draft.proto b/google/ads/googleads/v3/resources/campaign_draft.proto
index 582faa1c..6e3601b6 100644
--- a/google/ads/googleads/v3/resources/campaign_draft.proto
+++ b/google/ads/googleads/v3/resources/campaign_draft.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/campaign_draft_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,19 +40,29 @@ message CampaignDraft {
     pattern: "customers/{customer}/campaignDrafts/{campaign_draft}"
   };
 
-  // The resource name of the campaign draft.
+  // Immutable. The resource name of the campaign draft.
   // Campaign draft resource names have the form:
   //
   // `customers/{customer_id}/campaignDrafts/{base_campaign_id}~{draft_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignDraft"
+    }
+  ];
 
-  // The ID of the draft.
+  // Output only. The ID of the draft.
   //
   // This field is read-only.
-  google.protobuf.Int64Value draft_id = 2;
+  google.protobuf.Int64Value draft_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The base campaign to which the draft belongs.
-  google.protobuf.StringValue base_campaign = 3;
+  // Immutable. The base campaign to which the draft belongs.
+  google.protobuf.StringValue base_campaign = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
   // The name of the campaign draft.
   //
@@ -62,22 +73,27 @@ message CampaignDraft {
   // (code point 0xA) or carriage return (code point 0xD) characters.
   google.protobuf.StringValue name = 4;
 
-  // Resource name of the Campaign that results from overlaying the draft
+  // Output only. Resource name of the Campaign that results from overlaying the draft
   // changes onto the base campaign.
   //
   // This field is read-only.
-  google.protobuf.StringValue draft_campaign = 5;
+  google.protobuf.StringValue draft_campaign = 5 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The status of the campaign draft. This field is read-only.
+  // Output only. The status of the campaign draft. This field is read-only.
   //
   // When a new campaign draft is added, the status defaults to PROPOSED.
-  google.ads.googleads.v3.enums.CampaignDraftStatusEnum.CampaignDraftStatus status = 6;
+  google.ads.googleads.v3.enums.CampaignDraftStatusEnum.CampaignDraftStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether there is an experiment based on this draft currently serving.
-  google.protobuf.BoolValue has_experiment_running = 7;
+  // Output only. Whether there is an experiment based on this draft currently serving.
+  google.protobuf.BoolValue has_experiment_running = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the long-running operation that can be used to poll
+  // Output only. The resource name of the long-running operation that can be used to poll
   // for completion of draft promotion. This is only set if the draft promotion
   // is in progress or finished.
-  google.protobuf.StringValue long_running_operation = 8;
+  google.protobuf.StringValue long_running_operation = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/campaign_experiment.proto b/google/ads/googleads/v3/resources/campaign_experiment.proto
index 92379600..a02838ba 100644
--- a/google/ads/googleads/v3/resources/campaign_experiment.proto
+++ b/google/ads/googleads/v3/resources/campaign_experiment.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/campaign_experiment_status.proto";
 import "google/ads/googleads/v3/enums/campaign_experiment_traffic_split_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,19 +42,29 @@ message CampaignExperiment {
     pattern: "customers/{customer}/campaignExperiments/{campaign_experiment}"
   };
 
-  // The resource name of the campaign experiment.
+  // Immutable. The resource name of the campaign experiment.
   // Campaign experiment resource names have the form:
   //
   // `customers/{customer_id}/campaignExperiments/{campaign_experiment_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignExperiment"
+    }
+  ];
 
-  // The ID of the campaign experiment.
+  // Output only. The ID of the campaign experiment.
   //
   // This field is read-only.
-  google.protobuf.Int64Value id = 2;
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The campaign draft with staged changes to the base campaign.
-  google.protobuf.StringValue campaign_draft = 3;
+  // Immutable. The campaign draft with staged changes to the base campaign.
+  google.protobuf.StringValue campaign_draft = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignDraft"
+    }
+  ];
 
   // The name of the campaign experiment.
   //
@@ -68,24 +79,29 @@ message CampaignExperiment {
   // The description of the experiment.
   google.protobuf.StringValue description = 5;
 
-  // Share of traffic directed to experiment as a percent (must be between 1 and
+  // Immutable. Share of traffic directed to experiment as a percent (must be between 1 and
   // 99 inclusive. Base campaign receives the remainder of the traffic
   // (100 - traffic_split_percent). Required for create.
-  google.protobuf.Int64Value traffic_split_percent = 6;
+  google.protobuf.Int64Value traffic_split_percent = 6 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Determines the behavior of the traffic split.
-  google.ads.googleads.v3.enums.CampaignExperimentTrafficSplitTypeEnum.CampaignExperimentTrafficSplitType traffic_split_type = 7;
+  // Immutable. Determines the behavior of the traffic split.
+  google.ads.googleads.v3.enums.CampaignExperimentTrafficSplitTypeEnum.CampaignExperimentTrafficSplitType traffic_split_type = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The experiment campaign, as opposed to the base campaign.
-  google.protobuf.StringValue experiment_campaign = 8;
+  // Output only. The experiment campaign, as opposed to the base campaign.
+  google.protobuf.StringValue experiment_campaign = 8 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The status of the campaign experiment. This field is read-only.
-  google.ads.googleads.v3.enums.CampaignExperimentStatusEnum.CampaignExperimentStatus status = 9;
+  // Output only. The status of the campaign experiment. This field is read-only.
+  google.ads.googleads.v3.enums.CampaignExperimentStatusEnum.CampaignExperimentStatus status = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the long-running operation that can be used to poll
+  // Output only. The resource name of the long-running operation that can be used to poll
   // for completion of experiment create or promote. The most recent long
   // running operation is returned.
-  google.protobuf.StringValue long_running_operation = 10;
+  google.protobuf.StringValue long_running_operation = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Date when the campaign experiment starts. By default, the experiment starts
   // now or on the campaign's start date, whichever is later. If this field is
diff --git a/google/ads/googleads/v3/resources/campaign_extension_setting.proto b/google/ads/googleads/v3/resources/campaign_extension_setting.proto
index 8fc2c5d6..32758f7e 100644
--- a/google/ads/googleads/v3/resources/campaign_extension_setting.proto
+++ b/google/ads/googleads/v3/resources/campaign_extension_setting.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/extension_setting_device.proto";
 import "google/ads/googleads/v3/enums/extension_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,27 +41,39 @@ message CampaignExtensionSetting {
     pattern: "customers/{customer}/campaignExtensionSettings/{campaign_extension_setting}"
   };
 
-  // The resource name of the campaign extension setting.
+  // Immutable. The resource name of the campaign extension setting.
   // CampaignExtensionSetting resource names have the form:
   //
   // `customers/{customer_id}/campaignExtensionSettings/{campaign_id}~{extension_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignExtensionSetting"
+    }
+  ];
 
-  // The extension type of the customer extension setting.
-  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2;
+  // Immutable. The extension type of the customer extension setting.
+  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The resource name of the campaign. The linked extension feed items will
+  // Immutable. The resource name of the campaign. The linked extension feed items will
   // serve under this campaign.
   // Campaign resource names have the form:
   //
   // `customers/{customer_id}/campaigns/{campaign_id}`
-  google.protobuf.StringValue campaign = 3;
+  google.protobuf.StringValue campaign = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
   // The resource names of the extension feed items to serve under the campaign.
   // ExtensionFeedItem resource names have the form:
   //
   // `customers/{customer_id}/extensionFeedItems/{feed_item_id}`
-  repeated google.protobuf.StringValue extension_feed_items = 4;
+  repeated google.protobuf.StringValue extension_feed_items = 4 [(google.api.resource_reference) = {
+                                                                   type: "googleads.googleapis.com/ExtensionFeedItem"
+                                                                 }];
 
   // The device for which the extensions will serve. Optional.
   google.ads.googleads.v3.enums.ExtensionSettingDeviceEnum.ExtensionSettingDevice device = 5;
diff --git a/google/ads/googleads/v3/resources/campaign_feed.proto b/google/ads/googleads/v3/resources/campaign_feed.proto
index e61c0eab..7836d161 100644
--- a/google/ads/googleads/v3/resources/campaign_feed.proto
+++ b/google/ads/googleads/v3/resources/campaign_feed.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/matching_function.proto";
 import "google/ads/googleads/v3/enums/feed_link_status.proto";
 import "google/ads/googleads/v3/enums/placeholder_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,17 +42,32 @@ message CampaignFeed {
     pattern: "customers/{customer}/campaignFeeds/{campaign_feed}"
   };
 
-  // The resource name of the campaign feed.
+  // Immutable. The resource name of the campaign feed.
   // Campaign feed resource names have the form:
   //
   // `customers/{customer_id}/campaignFeeds/{campaign_id}~{feed_id}
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignFeed"
+    }
+  ];
 
-  // The feed to which the CampaignFeed belongs.
-  google.protobuf.StringValue feed = 2;
+  // Immutable. The feed to which the CampaignFeed belongs.
+  google.protobuf.StringValue feed = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // The campaign to which the CampaignFeed belongs.
-  google.protobuf.StringValue campaign = 3;
+  // Immutable. The campaign to which the CampaignFeed belongs.
+  google.protobuf.StringValue campaign = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
   // Indicates which placeholder types the feed may populate under the connected
   // campaign. Required.
@@ -62,7 +78,7 @@ message CampaignFeed {
   // Required.
   google.ads.googleads.v3.common.MatchingFunction matching_function = 5;
 
-  // Status of the campaign feed.
+  // Output only. Status of the campaign feed.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 6;
+  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/campaign_label.proto b/google/ads/googleads/v3/resources/campaign_label.proto
index f29ae1e3..8a92f5fa 100644
--- a/google/ads/googleads/v3/resources/campaign_label.proto
+++ b/google/ads/googleads/v3/resources/campaign_label.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,14 +39,29 @@ message CampaignLabel {
     pattern: "customers/{customer}/campaignLabels/{campaign_label}"
   };
 
-  // Name of the resource.
+  // Immutable. Name of the resource.
   // Campaign label resource names have the form:
   // `customers/{customer_id}/campaignLabels/{campaign_id}~{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignLabel"
+    }
+  ];
 
-  // The campaign to which the label is attached.
-  google.protobuf.StringValue campaign = 2;
+  // Immutable. The campaign to which the label is attached.
+  google.protobuf.StringValue campaign = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The label assigned to the campaign.
-  google.protobuf.StringValue label = 3;
+  // Immutable. The label assigned to the campaign.
+  google.protobuf.StringValue label = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Label"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/campaign_shared_set.proto b/google/ads/googleads/v3/resources/campaign_shared_set.proto
index deb133cc..2dab3234 100644
--- a/google/ads/googleads/v3/resources/campaign_shared_set.proto
+++ b/google/ads/googleads/v3/resources/campaign_shared_set.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/campaign_shared_set_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,23 +41,38 @@ message CampaignSharedSet {
     pattern: "customers/{customer}/campaignSharedSets/{campaign_shared_set}"
   };
 
-  // The resource name of the campaign shared set.
+  // Immutable. The resource name of the campaign shared set.
   // Campaign shared set resource names have the form:
   //
   // `customers/{customer_id}/campaignSharedSets/{campaign_id}~{shared_set_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignSharedSet"
+    }
+  ];
 
-  // The campaign to which the campaign shared set belongs.
-  google.protobuf.StringValue campaign = 3;
+  // Immutable. The campaign to which the campaign shared set belongs.
+  google.protobuf.StringValue campaign = 3 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The shared set associated with the campaign. This may be a negative keyword
+  // Immutable. The shared set associated with the campaign. This may be a negative keyword
   // shared set of another customer. This customer should be a manager of the
   // other customer, otherwise the campaign shared set will exist but have no
   // serving effect. Only negative keyword shared sets can be associated with
   // Shopping campaigns. Only negative placement shared sets can be associated
   // with Display mobile app campaigns.
-  google.protobuf.StringValue shared_set = 4;
+  google.protobuf.StringValue shared_set = 4 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/SharedSet"
+    }
+  ];
 
-  // The status of this campaign shared set. Read only.
-  google.ads.googleads.v3.enums.CampaignSharedSetStatusEnum.CampaignSharedSetStatus status = 2;
+  // Output only. The status of this campaign shared set. Read only.
+  google.ads.googleads.v3.enums.CampaignSharedSetStatusEnum.CampaignSharedSetStatus status = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/carrier_constant.proto b/google/ads/googleads/v3/resources/carrier_constant.proto
index 0f350f3a..b892f3e4 100644
--- a/google/ads/googleads/v3/resources/carrier_constant.proto
+++ b/google/ads/googleads/v3/resources/carrier_constant.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,19 +39,24 @@ message CarrierConstant {
     pattern: "carrierConstants/{carrier_constant}"
   };
 
-  // The resource name of the carrier criterion.
+  // Output only. The resource name of the carrier criterion.
   // Carrier criterion resource names have the form:
   //
   // `carrierConstants/{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CarrierConstant"
+    }
+  ];
 
-  // The ID of the carrier criterion.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the carrier criterion.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The full name of the carrier in English.
-  google.protobuf.StringValue name = 3;
+  // Output only. The full name of the carrier in English.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The country code of the country where the carrier is located, e.g., "AR",
+  // Output only. The country code of the country where the carrier is located, e.g., "AR",
   // "FR", etc.
-  google.protobuf.StringValue country_code = 4;
+  google.protobuf.StringValue country_code = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/change_status.proto b/google/ads/googleads/v3/resources/change_status.proto
index 77d81ea0..9c54a236 100644
--- a/google/ads/googleads/v3/resources/change_status.proto
+++ b/google/ads/googleads/v3/resources/change_status.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/change_status_operation.proto";
 import "google/ads/googleads/v3/enums/change_status_resource_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,50 +41,105 @@ message ChangeStatus {
     pattern: "customers/{customer}/changeStatus/{change_status}"
   };
 
-  // The resource name of the change status.
+  // Output only. The resource name of the change status.
   // Change status resource names have the form:
   //
   // `customers/{customer_id}/changeStatus/{change_status_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ChangeStatus"
+    }
+  ];
 
-  // Time at which the most recent change has occurred on this resource.
-  google.protobuf.StringValue last_change_date_time = 3;
+  // Output only. Time at which the most recent change has occurred on this resource.
+  google.protobuf.StringValue last_change_date_time = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Represents the type of the changed resource. This dictates what fields
+  // Output only. Represents the type of the changed resource. This dictates what fields
   // will be set. For example, for AD_GROUP, campaign and ad_group fields will
   // be set.
-  google.ads.googleads.v3.enums.ChangeStatusResourceTypeEnum.ChangeStatusResourceType resource_type = 4;
+  google.ads.googleads.v3.enums.ChangeStatusResourceTypeEnum.ChangeStatusResourceType resource_type = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The Campaign affected by this change.
-  google.protobuf.StringValue campaign = 5;
+  // Output only. The Campaign affected by this change.
+  google.protobuf.StringValue campaign = 5 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The AdGroup affected by this change.
-  google.protobuf.StringValue ad_group = 6;
+  // Output only. The AdGroup affected by this change.
+  google.protobuf.StringValue ad_group = 6 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // Represents the status of the changed resource.
-  google.ads.googleads.v3.enums.ChangeStatusOperationEnum.ChangeStatusOperation resource_status = 8;
+  // Output only. Represents the status of the changed resource.
+  google.ads.googleads.v3.enums.ChangeStatusOperationEnum.ChangeStatusOperation resource_status = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The AdGroupAd affected by this change.
-  google.protobuf.StringValue ad_group_ad = 9;
+  // Output only. The AdGroupAd affected by this change.
+  google.protobuf.StringValue ad_group_ad = 9 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAd"
+    }
+  ];
 
-  // The AdGroupCriterion affected by this change.
-  google.protobuf.StringValue ad_group_criterion = 10;
+  // Output only. The AdGroupCriterion affected by this change.
+  google.protobuf.StringValue ad_group_criterion = 10 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupCriterion"
+    }
+  ];
 
-  // The CampaignCriterion affected by this change.
-  google.protobuf.StringValue campaign_criterion = 11;
+  // Output only. The CampaignCriterion affected by this change.
+  google.protobuf.StringValue campaign_criterion = 11 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignCriterion"
+    }
+  ];
 
-  // The Feed affected by this change.
-  google.protobuf.StringValue feed = 12;
+  // Output only. The Feed affected by this change.
+  google.protobuf.StringValue feed = 12 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // The FeedItem affected by this change.
-  google.protobuf.StringValue feed_item = 13;
+  // Output only. The FeedItem affected by this change.
+  google.protobuf.StringValue feed_item = 13 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedItem"
+    }
+  ];
 
-  // The AdGroupFeed affected by this change.
-  google.protobuf.StringValue ad_group_feed = 14;
+  // Output only. The AdGroupFeed affected by this change.
+  google.protobuf.StringValue ad_group_feed = 14 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupFeed"
+    }
+  ];
 
-  // The CampaignFeed affected by this change.
-  google.protobuf.StringValue campaign_feed = 15;
+  // Output only. The CampaignFeed affected by this change.
+  google.protobuf.StringValue campaign_feed = 15 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignFeed"
+    }
+  ];
 
-  // The AdGroupBidModifier affected by this change.
-  google.protobuf.StringValue ad_group_bid_modifier = 16;
+  // Output only. The AdGroupBidModifier affected by this change.
+  google.protobuf.StringValue ad_group_bid_modifier = 16 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupBidModifier"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/click_view.proto b/google/ads/googleads/v3/resources/click_view.proto
index de6548f3..216e207e 100644
--- a/google/ads/googleads/v3/resources/click_view.proto
+++ b/google/ads/googleads/v3/resources/click_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/click_location.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -44,26 +45,36 @@ message ClickView {
     pattern: "customers/{customer}/clickViews/{click_view}"
   };
 
-  // The resource name of the click view.
+  // Output only. The resource name of the click view.
   // Click view resource names have the form:
   //
   // `customers/{customer_id}/clickViews/{date (yyyy-MM-dd)}~{gclid}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ClickView"
+    }
+  ];
 
-  // The Google Click ID.
-  google.protobuf.StringValue gclid = 2;
+  // Output only. The Google Click ID.
+  google.protobuf.StringValue gclid = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The location criteria matching the area of interest associated with the
+  // Output only. The location criteria matching the area of interest associated with the
   // impression.
-  google.ads.googleads.v3.common.ClickLocation area_of_interest = 3;
+  google.ads.googleads.v3.common.ClickLocation area_of_interest = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The location criteria matching the location of presence associated with the
+  // Output only. The location criteria matching the location of presence associated with the
   // impression.
-  google.ads.googleads.v3.common.ClickLocation location_of_presence = 4;
+  google.ads.googleads.v3.common.ClickLocation location_of_presence = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Page number in search results where the ad was shown.
-  google.protobuf.Int64Value page_number = 5;
+  // Output only. Page number in search results where the ad was shown.
+  google.protobuf.Int64Value page_number = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The associated ad.
-  google.protobuf.StringValue ad_group_ad = 7;
+  // Output only. The associated ad.
+  google.protobuf.StringValue ad_group_ad = 7 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroupAd"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/conversion_action.proto b/google/ads/googleads/v3/resources/conversion_action.proto
index 1aa33fcf..b5a33d3c 100644
--- a/google/ads/googleads/v3/resources/conversion_action.proto
+++ b/google/ads/googleads/v3/resources/conversion_action.proto
@@ -23,6 +23,7 @@ import "google/ads/googleads/v3/enums/conversion_action_counting_type.proto";
 import "google/ads/googleads/v3/enums/conversion_action_status.proto";
 import "google/ads/googleads/v3/enums/conversion_action_type.proto";
 import "google/ads/googleads/v3/enums/data_driven_model_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -50,9 +51,9 @@ message ConversionAction {
     // The attribution model type of this conversion action.
     google.ads.googleads.v3.enums.AttributionModelEnum.AttributionModel attribution_model = 1;
 
-    // The status of the data-driven attribution model for the conversion
+    // Output only. The status of the data-driven attribution model for the conversion
     // action.
-    google.ads.googleads.v3.enums.DataDrivenModelStatusEnum.DataDrivenModelStatus data_driven_model_status = 2;
+    google.ads.googleads.v3.enums.DataDrivenModelStatusEnum.DataDrivenModelStatus data_driven_model_status = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // Settings related to the value for conversion events associated with this
@@ -74,14 +75,19 @@ message ConversionAction {
     google.protobuf.BoolValue always_use_default_value = 3;
   }
 
-  // The resource name of the conversion action.
+  // Immutable. The resource name of the conversion action.
   // Conversion action resource names have the form:
   //
   // `customers/{customer_id}/conversionActions/{conversion_action_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ConversionAction"
+    }
+  ];
 
-  // The ID of the conversion action.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the conversion action.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the conversion action.
   //
@@ -92,15 +98,15 @@ message ConversionAction {
   // The status of this conversion action for conversion event accrual.
   google.ads.googleads.v3.enums.ConversionActionStatusEnum.ConversionActionStatus status = 4;
 
-  // The type of this conversion action.
-  google.ads.googleads.v3.enums.ConversionActionTypeEnum.ConversionActionType type = 5;
+  // Immutable. The type of this conversion action.
+  google.ads.googleads.v3.enums.ConversionActionTypeEnum.ConversionActionType type = 5 [(google.api.field_behavior) = IMMUTABLE];
 
   // The category of conversions reported for this conversion action.
   google.ads.googleads.v3.enums.ConversionActionCategoryEnum.ConversionActionCategory category = 6;
 
-  // The resource name of the conversion action owner customer, or null if this
+  // Output only. The resource name of the conversion action owner customer, or null if this
   // is a system-defined conversion action.
-  google.protobuf.StringValue owner_customer = 7;
+  google.protobuf.StringValue owner_customer = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Whether this conversion action should be included in the "conversions"
   // metric.
@@ -124,8 +130,8 @@ message ConversionAction {
   // Settings related to this conversion action's attribution model.
   AttributionModelSettings attribution_model_settings = 13;
 
-  // The snippets used for tracking conversions.
-  repeated google.ads.googleads.v3.common.TagSnippet tag_snippets = 14;
+  // Output only. The snippets used for tracking conversions.
+  repeated google.ads.googleads.v3.common.TagSnippet tag_snippets = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The phone call duration in seconds after which a conversion should be
   // reported for this conversion action.
diff --git a/google/ads/googleads/v3/resources/currency_constant.proto b/google/ads/googleads/v3/resources/currency_constant.proto
index 270c6083..69be8065 100644
--- a/google/ads/googleads/v3/resources/currency_constant.proto
+++ b/google/ads/googleads/v3/resources/currency_constant.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,22 +39,27 @@ message CurrencyConstant {
     pattern: "currencyConstants/{currency_constant}"
   };
 
-  // The resource name of the currency constant.
+  // Output only. The resource name of the currency constant.
   // Currency constant resource names have the form:
   //
   // `currencyConstants/{currency_code}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CurrencyConstant"
+    }
+  ];
 
-  // ISO 4217 three-letter currency code, e.g. "USD"
-  google.protobuf.StringValue code = 2;
+  // Output only. ISO 4217 three-letter currency code, e.g. "USD"
+  google.protobuf.StringValue code = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Full English name of the currency.
-  google.protobuf.StringValue name = 3;
+  // Output only. Full English name of the currency.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Standard symbol for describing this currency, e.g. '$' for US Dollars.
-  google.protobuf.StringValue symbol = 4;
+  // Output only. Standard symbol for describing this currency, e.g. '$' for US Dollars.
+  google.protobuf.StringValue symbol = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The billable unit for this currency. Billed amounts should be multiples of
+  // Output only. The billable unit for this currency. Billed amounts should be multiples of
   // this value.
-  google.protobuf.Int64Value billable_unit_micros = 5;
+  google.protobuf.Int64Value billable_unit_micros = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/custom_interest.proto b/google/ads/googleads/v3/resources/custom_interest.proto
index bfe3f051..c2824dec 100644
--- a/google/ads/googleads/v3/resources/custom_interest.proto
+++ b/google/ads/googleads/v3/resources/custom_interest.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/enums/custom_interest_member_type.proto";
 import "google/ads/googleads/v3/enums/custom_interest_status.proto";
 import "google/ads/googleads/v3/enums/custom_interest_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,14 +42,19 @@ message CustomInterest {
     pattern: "customers/{customer}/customInterests/{custom_interest}"
   };
 
-  // The resource name of the custom interest.
+  // Immutable. The resource name of the custom interest.
   // Custom interest resource names have the form:
   //
   // `customers/{customer_id}/customInterests/{custom_interest_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomInterest"
+    }
+  ];
 
-  // Id of the custom interest.
-  google.protobuf.Int64Value id = 2;
+  // Output only. Id of the custom interest.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Status of this custom interest. Indicates whether the custom interest is
   // enabled or removed.
diff --git a/google/ads/googleads/v3/resources/customer.proto b/google/ads/googleads/v3/resources/customer.proto
index 89d074be..7e4d3af1 100644
--- a/google/ads/googleads/v3/resources/customer.proto
+++ b/google/ads/googleads/v3/resources/customer.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/customer_pay_per_conversion_eligibility_failure_reason.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,25 +40,30 @@ message Customer {
     pattern: "customers/{customer}"
   };
 
-  // The resource name of the customer.
+  // Immutable. The resource name of the customer.
   // Customer resource names have the form:
   //
   // `customers/{customer_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Customer"
+    }
+  ];
 
-  // The ID of the customer.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the customer.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Optional, non-unique descriptive name of the customer.
   google.protobuf.StringValue descriptive_name = 4;
 
-  // The currency in which the account operates.
+  // Immutable. The currency in which the account operates.
   // A subset of the currency codes from the ISO 4217 standard is
   // supported.
-  google.protobuf.StringValue currency_code = 5;
+  google.protobuf.StringValue currency_code = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The local timezone ID of the customer.
-  google.protobuf.StringValue time_zone = 6;
+  // Immutable. The local timezone ID of the customer.
+  google.protobuf.StringValue time_zone = 6 [(google.api.field_behavior) = IMMUTABLE];
 
   // The URL template for constructing a tracking URL out of parameters.
   google.protobuf.StringValue tracking_url_template = 7;
@@ -68,29 +74,29 @@ message Customer {
   // Whether auto-tagging is enabled for the customer.
   google.protobuf.BoolValue auto_tagging_enabled = 8;
 
-  // Whether the Customer has a Partners program badge. If the Customer is not
+  // Output only. Whether the Customer has a Partners program badge. If the Customer is not
   // associated with the Partners program, this will be false. For more
   // information, see https://support.google.com/partners/answer/3125774.
-  google.protobuf.BoolValue has_partners_badge = 9;
+  google.protobuf.BoolValue has_partners_badge = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the customer is a manager.
-  google.protobuf.BoolValue manager = 12;
+  // Output only. Whether the customer is a manager.
+  google.protobuf.BoolValue manager = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the customer is a test account.
-  google.protobuf.BoolValue test_account = 13;
+  // Output only. Whether the customer is a test account.
+  google.protobuf.BoolValue test_account = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Call reporting setting for a customer.
   CallReportingSetting call_reporting_setting = 10;
 
-  // Conversion tracking setting for a customer.
-  ConversionTrackingSetting conversion_tracking_setting = 14;
+  // Output only. Conversion tracking setting for a customer.
+  ConversionTrackingSetting conversion_tracking_setting = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Remarketing setting for a customer.
-  RemarketingSetting remarketing_setting = 15;
+  // Output only. Remarketing setting for a customer.
+  RemarketingSetting remarketing_setting = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Reasons why the customer is not eligible to use PaymentMode.CONVERSIONS. If
+  // Output only. Reasons why the customer is not eligible to use PaymentMode.CONVERSIONS. If
   // the list is empty, the customer is eligible. This field is read-only.
-  repeated google.ads.googleads.v3.enums.CustomerPayPerConversionEligibilityFailureReasonEnum.CustomerPayPerConversionEligibilityFailureReason pay_per_conversion_eligibility_failure_reasons = 16;
+  repeated google.ads.googleads.v3.enums.CustomerPayPerConversionEligibilityFailureReasonEnum.CustomerPayPerConversionEligibilityFailureReason pay_per_conversion_eligibility_failure_reasons = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Call reporting setting for a customer.
@@ -105,26 +111,28 @@ message CallReportingSetting {
   // Customer-level call conversion action to attribute a call conversion to.
   // If not set a default conversion action is used. Only in effect when
   // call_conversion_reporting_enabled is set to true.
-  google.protobuf.StringValue call_conversion_action = 9;
+  google.protobuf.StringValue call_conversion_action = 9 [(google.api.resource_reference) = {
+                                                            type: "googleads.googleapis.com/ConversionAction"
+                                                          }];
 }
 
 // A collection of customer-wide settings related to Google Ads Conversion
 // Tracking.
 message ConversionTrackingSetting {
-  // The conversion tracking id used for this account. This id is automatically
+  // Output only. The conversion tracking id used for this account. This id is automatically
   // assigned after any conversion tracking feature is used. If the customer
   // doesn't use conversion tracking, this is 0. This field is read-only.
-  google.protobuf.Int64Value conversion_tracking_id = 1;
+  google.protobuf.Int64Value conversion_tracking_id = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The conversion tracking id of the customer's manager. This is set when the
+  // Output only. The conversion tracking id of the customer's manager. This is set when the
   // customer is opted into cross account conversion tracking, and it overrides
   // conversion_tracking_id. This field can only be managed through the Google
   // Ads UI. This field is read-only.
-  google.protobuf.Int64Value cross_account_conversion_tracking_id = 2;
+  google.protobuf.Int64Value cross_account_conversion_tracking_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Remarketing setting for a customer.
 message RemarketingSetting {
-  // The Google global site tag.
-  google.protobuf.StringValue google_global_site_tag = 1;
+  // Output only. The Google global site tag.
+  google.protobuf.StringValue google_global_site_tag = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/customer_client.proto b/google/ads/googleads/v3/resources/customer_client.proto
index 23dd9912..d04d4cad 100644
--- a/google/ads/googleads/v3/resources/customer_client.proto
+++ b/google/ads/googleads/v3/resources/customer_client.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,40 +41,45 @@ message CustomerClient {
     pattern: "customers/{customer}/customerClients/{customer_client}"
   };
 
-  // The resource name of the customer client.
+  // Output only. The resource name of the customer client.
   // CustomerClient resource names have the form:
   // `customers/{customer_id}/customerClients/{client_customer_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerClient"
+    }
+  ];
 
-  // The resource name of the client-customer which is linked to
+  // Output only. The resource name of the client-customer which is linked to
   // the given customer. Read only.
-  google.protobuf.StringValue client_customer = 3;
+  google.protobuf.StringValue client_customer = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Specifies whether this is a
+  // Output only. Specifies whether this is a
   // [hidden account](https://support.google.com/google-ads/answer/7519830).
   // Read only.
-  google.protobuf.BoolValue hidden = 4;
+  google.protobuf.BoolValue hidden = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Distance between given customer and client. For self link, the level value
+  // Output only. Distance between given customer and client. For self link, the level value
   // will be 0. Read only.
-  google.protobuf.Int64Value level = 5;
+  google.protobuf.Int64Value level = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Common Locale Data Repository (CLDR) string representation of the
+  // Output only. Common Locale Data Repository (CLDR) string representation of the
   // time zone of the client, e.g. America/Los_Angeles. Read only.
-  google.protobuf.StringValue time_zone = 6;
+  google.protobuf.StringValue time_zone = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Identifies if the client is a test account. Read only.
-  google.protobuf.BoolValue test_account = 7;
+  // Output only. Identifies if the client is a test account. Read only.
+  google.protobuf.BoolValue test_account = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Identifies if the client is a manager. Read only.
-  google.protobuf.BoolValue manager = 8;
+  // Output only. Identifies if the client is a manager. Read only.
+  google.protobuf.BoolValue manager = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Descriptive name for the client. Read only.
-  google.protobuf.StringValue descriptive_name = 9;
+  // Output only. Descriptive name for the client. Read only.
+  google.protobuf.StringValue descriptive_name = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Currency code (e.g. 'USD', 'EUR') for the client. Read only.
-  google.protobuf.StringValue currency_code = 10;
+  // Output only. Currency code (e.g. 'USD', 'EUR') for the client. Read only.
+  google.protobuf.StringValue currency_code = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ID of the client customer. Read only.
-  google.protobuf.Int64Value id = 11;
+  // Output only. The ID of the client customer. Read only.
+  google.protobuf.Int64Value id = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/customer_client_link.proto b/google/ads/googleads/v3/resources/customer_client_link.proto
index 28c93e05..c0c8dd66 100644
--- a/google/ads/googleads/v3/resources/customer_client_link.proto
+++ b/google/ads/googleads/v3/resources/customer_client_link.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/manager_link_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,16 +40,21 @@ message CustomerClientLink {
     pattern: "customers/{customer}/customerClientLinks/{customer_client_link}"
   };
 
-  // Name of the resource.
+  // Immutable. Name of the resource.
   // CustomerClientLink resource names have the form:
   // `customers/{customer_id}/customerClientLinks/{client_customer_id}~{manager_link_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerClientLink"
+    }
+  ];
 
-  // The client customer linked to this customer.
-  google.protobuf.StringValue client_customer = 3;
+  // Immutable. The client customer linked to this customer.
+  google.protobuf.StringValue client_customer = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-  // This is uniquely identifies a customer client link. Read only.
-  google.protobuf.Int64Value manager_link_id = 4;
+  // Output only. This is uniquely identifies a customer client link. Read only.
+  google.protobuf.Int64Value manager_link_id = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // This is the status of the link between client and manager.
   google.ads.googleads.v3.enums.ManagerLinkStatusEnum.ManagerLinkStatus status = 5;
diff --git a/google/ads/googleads/v3/resources/customer_extension_setting.proto b/google/ads/googleads/v3/resources/customer_extension_setting.proto
index 557a856a..c4c1ef8b 100644
--- a/google/ads/googleads/v3/resources/customer_extension_setting.proto
+++ b/google/ads/googleads/v3/resources/customer_extension_setting.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/extension_setting_device.proto";
 import "google/ads/googleads/v3/enums/extension_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,20 +41,27 @@ message CustomerExtensionSetting {
     pattern: "customers/{customer}/customerExtensionSettings/{customer_extension_setting}"
   };
 
-  // The resource name of the customer extension setting.
+  // Immutable. The resource name of the customer extension setting.
   // CustomerExtensionSetting resource names have the form:
   //
   // `customers/{customer_id}/customerExtensionSettings/{extension_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerExtensionSetting"
+    }
+  ];
 
-  // The extension type of the customer extension setting.
-  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2;
+  // Immutable. The extension type of the customer extension setting.
+  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 2 [(google.api.field_behavior) = IMMUTABLE];
 
   // The resource names of the extension feed items to serve under the customer.
   // ExtensionFeedItem resource names have the form:
   //
   // `customers/{customer_id}/extensionFeedItems/{feed_item_id}`
-  repeated google.protobuf.StringValue extension_feed_items = 3;
+  repeated google.protobuf.StringValue extension_feed_items = 3 [(google.api.resource_reference) = {
+                                                                   type: "googleads.googleapis.com/ExtensionFeedItem"
+                                                                 }];
 
   // The device for which the extensions will serve. Optional.
   google.ads.googleads.v3.enums.ExtensionSettingDeviceEnum.ExtensionSettingDevice device = 4;
diff --git a/google/ads/googleads/v3/resources/customer_feed.proto b/google/ads/googleads/v3/resources/customer_feed.proto
index 5246c004..aacc6938 100644
--- a/google/ads/googleads/v3/resources/customer_feed.proto
+++ b/google/ads/googleads/v3/resources/customer_feed.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.resources;
 import "google/ads/googleads/v3/common/matching_function.proto";
 import "google/ads/googleads/v3/enums/feed_link_status.proto";
 import "google/ads/googleads/v3/enums/placeholder_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,14 +42,24 @@ message CustomerFeed {
     pattern: "customers/{customer}/customerFeeds/{customer_feed}"
   };
 
-  // The resource name of the customer feed.
+  // Immutable. The resource name of the customer feed.
   // Customer feed resource names have the form:
   //
   // `customers/{customer_id}/customerFeeds/{feed_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerFeed"
+    }
+  ];
 
-  // The feed being linked to the customer.
-  google.protobuf.StringValue feed = 2;
+  // Immutable. The feed being linked to the customer.
+  google.protobuf.StringValue feed = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
   // Indicates which placeholder types the feed may populate under the connected
   // customer. Required.
@@ -59,7 +70,7 @@ message CustomerFeed {
   // Required.
   google.ads.googleads.v3.common.MatchingFunction matching_function = 4;
 
-  // Status of the customer feed.
+  // Output only. Status of the customer feed.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 5;
+  google.ads.googleads.v3.enums.FeedLinkStatusEnum.FeedLinkStatus status = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/customer_label.proto b/google/ads/googleads/v3/resources/customer_label.proto
index 7da08d8d..c36f4c38 100644
--- a/google/ads/googleads/v3/resources/customer_label.proto
+++ b/google/ads/googleads/v3/resources/customer_label.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,18 +41,23 @@ message CustomerLabel {
     pattern: "customers/{customer}/customerLabels/{customer_label}"
   };
 
-  // Name of the resource.
+  // Immutable. Name of the resource.
   // Customer label resource names have the form:
   // `customers/{customer_id}/customerLabels/{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerLabel"
+    }
+  ];
 
-  // The resource name of the customer to which the label is attached.
+  // Output only. The resource name of the customer to which the label is attached.
   // Read only.
-  google.protobuf.StringValue customer = 2;
+  google.protobuf.StringValue customer = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the label assigned to the customer.
+  // Output only. The resource name of the label assigned to the customer.
   //
   // Note: the Customer ID portion of the label resource name is not
   // validated when creating a new CustomerLabel.
-  google.protobuf.StringValue label = 3;
+  google.protobuf.StringValue label = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/customer_manager_link.proto b/google/ads/googleads/v3/resources/customer_manager_link.proto
index f684662e..9843d9d3 100644
--- a/google/ads/googleads/v3/resources/customer_manager_link.proto
+++ b/google/ads/googleads/v3/resources/customer_manager_link.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/manager_link_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,16 +40,21 @@ message CustomerManagerLink {
     pattern: "customers/{customer}/customerManagerLinks/{customer_manager_link}"
   };
 
-  // Name of the resource.
+  // Immutable. Name of the resource.
   // CustomerManagerLink resource names have the form:
   // `customers/{customer_id}/customerManagerLinks/{manager_customer_id}~{manager_link_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerManagerLink"
+    }
+  ];
 
-  // The manager customer linked to the customer.
-  google.protobuf.StringValue manager_customer = 3;
+  // Output only. The manager customer linked to the customer.
+  google.protobuf.StringValue manager_customer = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // ID of the customer-manager link. This field is read only.
-  google.protobuf.Int64Value manager_link_id = 4;
+  // Output only. ID of the customer-manager link. This field is read only.
+  google.protobuf.Int64Value manager_link_id = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Status of the link between the customer and the manager.
   google.ads.googleads.v3.enums.ManagerLinkStatusEnum.ManagerLinkStatus status = 5;
diff --git a/google/ads/googleads/v3/resources/customer_negative_criterion.proto b/google/ads/googleads/v3/resources/customer_negative_criterion.proto
index e989bd51..521aabcd 100644
--- a/google/ads/googleads/v3/resources/customer_negative_criterion.proto
+++ b/google/ads/googleads/v3/resources/customer_negative_criterion.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/criteria.proto";
 import "google/ads/googleads/v3/enums/criterion_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,38 +41,43 @@ message CustomerNegativeCriterion {
     pattern: "customers/{customer}/customerNegativeCriteria/{customer_negative_criterion}"
   };
 
-  // The resource name of the customer negative criterion.
+  // Immutable. The resource name of the customer negative criterion.
   // Customer negative criterion resource names have the form:
   //
   // `customers/{customer_id}/customerNegativeCriteria/{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CustomerNegativeCriterion"
+    }
+  ];
 
-  // The ID of the criterion.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the criterion.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of the criterion.
-  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 3;
+  // Output only. The type of the criterion.
+  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The customer negative criterion.
   //
   // Exactly one must be set.
   oneof criterion {
-    // ContentLabel.
-    google.ads.googleads.v3.common.ContentLabelInfo content_label = 4;
+    // Immutable. ContentLabel.
+    google.ads.googleads.v3.common.ContentLabelInfo content_label = 4 [(google.api.field_behavior) = IMMUTABLE];
 
-    // MobileApplication.
-    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 5;
+    // Immutable. MobileApplication.
+    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-    // MobileAppCategory.
-    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 6;
+    // Immutable. MobileAppCategory.
+    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 6 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Placement.
-    google.ads.googleads.v3.common.PlacementInfo placement = 7;
+    // Immutable. Placement.
+    google.ads.googleads.v3.common.PlacementInfo placement = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Video.
-    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 8;
+    // Immutable. YouTube Video.
+    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Channel.
-    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 9;
+    // Immutable. YouTube Channel.
+    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 9 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/detail_placement_view.proto b/google/ads/googleads/v3/resources/detail_placement_view.proto
index 6ca6f5c8..b34526ab 100644
--- a/google/ads/googleads/v3/resources/detail_placement_view.proto
+++ b/google/ads/googleads/v3/resources/detail_placement_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/placement_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,28 +40,33 @@ message DetailPlacementView {
     pattern: "customers/{customer}/detailPlacementViews/{detail_placement_view}"
   };
 
-  // The resource name of the detail placement view.
+  // Output only. The resource name of the detail placement view.
   // Detail placement view resource names have the form:
   //
   // `customers/{customer_id}/detailPlacementViews/{ad_group_id}~{base64_placement}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/DetailPlacementView"
+    }
+  ];
 
-  // The automatic placement string at detail level, e. g. website URL, mobile
+  // Output only. The automatic placement string at detail level, e. g. website URL, mobile
   // application ID, or a YouTube video ID.
-  google.protobuf.StringValue placement = 2;
+  google.protobuf.StringValue placement = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The display name is URL name for websites, YouTube video name for YouTube
+  // Output only. The display name is URL name for websites, YouTube video name for YouTube
   // videos, and translated mobile app name for mobile apps.
-  google.protobuf.StringValue display_name = 3;
+  google.protobuf.StringValue display_name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // URL of the group placement, e.g. domain, link to the mobile application in
+  // Output only. URL of the group placement, e.g. domain, link to the mobile application in
   // app store, or a YouTube channel URL.
-  google.protobuf.StringValue group_placement_target_url = 4;
+  google.protobuf.StringValue group_placement_target_url = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // URL of the placement, e.g. website, link to the mobile application in app
+  // Output only. URL of the placement, e.g. website, link to the mobile application in app
   // store, or a YouTube video URL.
-  google.protobuf.StringValue target_url = 5;
+  google.protobuf.StringValue target_url = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Type of the placement, e.g. Website, YouTube Video, and Mobile Application.
-  google.ads.googleads.v3.enums.PlacementTypeEnum.PlacementType placement_type = 6;
+  // Output only. Type of the placement, e.g. Website, YouTube Video, and Mobile Application.
+  google.ads.googleads.v3.enums.PlacementTypeEnum.PlacementType placement_type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/display_keyword_view.proto b/google/ads/googleads/v3/resources/display_keyword_view.proto
index 633f39df..ef6a16f7 100644
--- a/google/ads/googleads/v3/resources/display_keyword_view.proto
+++ b/google/ads/googleads/v3/resources/display_keyword_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message DisplayKeywordView {
     pattern: "customers/{customer}/displayKeywordViews/{display_keyword_view}"
   };
 
-  // The resource name of the display keyword view.
+  // Output only. The resource name of the display keyword view.
   // Display Keyword view resource names have the form:
   //
   // `customers/{customer_id}/displayKeywordViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/DisplayKeywordView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/distance_view.proto b/google/ads/googleads/v3/resources/distance_view.proto
index 83636856..d334934b 100644
--- a/google/ads/googleads/v3/resources/distance_view.proto
+++ b/google/ads/googleads/v3/resources/distance_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/distance_bucket.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,15 +44,20 @@ message DistanceView {
     pattern: "customers/{customer}/distanceViews/{distance_view}"
   };
 
-  // The resource name of the distance view.
+  // Output only. The resource name of the distance view.
   // Distance view resource names have the form:
   //
   // `customers/{customer_id}/distanceViews/1~{distance_bucket}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/DistanceView"
+    }
+  ];
 
-  // Grouping of user distance from location extensions.
-  google.ads.googleads.v3.enums.DistanceBucketEnum.DistanceBucket distance_bucket = 2;
+  // Output only. Grouping of user distance from location extensions.
+  google.ads.googleads.v3.enums.DistanceBucketEnum.DistanceBucket distance_bucket = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // True if the DistanceBucket is using the metric system, false otherwise.
-  google.protobuf.BoolValue metric_system = 3;
+  // Output only. True if the DistanceBucket is using the metric system, false otherwise.
+  google.protobuf.BoolValue metric_system = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/domain_category.proto b/google/ads/googleads/v3/resources/domain_category.proto
index eac1845b..95faa4dc 100644
--- a/google/ads/googleads/v3/resources/domain_category.proto
+++ b/google/ads/googleads/v3/resources/domain_category.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,40 +42,50 @@ message DomainCategory {
     pattern: "customers/{customer}/domainCategories/{domain_category}"
   };
 
-  // The resource name of the domain category.
+  // Output only. The resource name of the domain category.
   // Domain category resource names have the form:
   //
   // `customers/{customer_id}/domainCategories/{campaign_id}~{category_base64}~{language_code}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/DomainCategory"
+    }
+  ];
 
-  // The campaign this category is recommended for.
-  google.protobuf.StringValue campaign = 2;
+  // Output only. The campaign this category is recommended for.
+  google.protobuf.StringValue campaign = 2 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // Recommended category for the website domain. e.g. if you have a website
+  // Output only. Recommended category for the website domain. e.g. if you have a website
   // about electronics, the categories could be "cameras", "televisions", etc.
-  google.protobuf.StringValue category = 3;
+  google.protobuf.StringValue category = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The language code specifying the language of the website. e.g. "en" for
+  // Output only. The language code specifying the language of the website. e.g. "en" for
   // English. The language can be specified in the DynamicSearchAdsSetting
   // required for dynamic search ads. This is the language of the pages from
   // your website that you want Google Ads to find, create ads for,
   // and match searches with.
-  google.protobuf.StringValue language_code = 4;
+  google.protobuf.StringValue language_code = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The domain for the website. The domain can be specified in the
+  // Output only. The domain for the website. The domain can be specified in the
   // DynamicSearchAdsSetting required for dynamic search ads.
-  google.protobuf.StringValue domain = 5;
+  google.protobuf.StringValue domain = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Fraction of pages on your site that this category matches.
-  google.protobuf.DoubleValue coverage_fraction = 6;
+  // Output only. Fraction of pages on your site that this category matches.
+  google.protobuf.DoubleValue coverage_fraction = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The position of this category in the set of categories. Lower numbers
+  // Output only. The position of this category in the set of categories. Lower numbers
   // indicate a better match for the domain. null indicates not recommended.
-  google.protobuf.Int64Value category_rank = 7;
+  google.protobuf.Int64Value category_rank = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Indicates whether this category has sub-categories.
-  google.protobuf.BoolValue has_children = 8;
+  // Output only. Indicates whether this category has sub-categories.
+  google.protobuf.BoolValue has_children = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The recommended cost per click for the category.
-  google.protobuf.Int64Value recommended_cpc_bid_micros = 9;
+  // Output only. The recommended cost per click for the category.
+  google.protobuf.Int64Value recommended_cpc_bid_micros = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/dynamic_search_ads_search_term_view.proto b/google/ads/googleads/v3/resources/dynamic_search_ads_search_term_view.proto
index 46ba0f71..688d4af4 100644
--- a/google/ads/googleads/v3/resources/dynamic_search_ads_search_term_view.proto
+++ b/google/ads/googleads/v3/resources/dynamic_search_ads_search_term_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,44 +39,49 @@ message DynamicSearchAdsSearchTermView {
     pattern: "customers/{customer}/dynamicSearchAdsSearchTermViews/{dynamic_search_ads_search_term_view}"
   };
 
-  // The resource name of the dynamic search ads search term view.
+  // Output only. The resource name of the dynamic search ads search term view.
   // Dynamic search ads search term view resource names have the form:
   //
   // `customers/{customer_id}/dynamicSearchAdsSearchTermViews/{ad_group_id}~{search_term_fp}~{headline_fp}~{landing_page_fp}~{page_url_fp}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/DynamicSearchAdsSearchTermView"
+    }
+  ];
 
-  // Search term
+  // Output only. Search term
   //
   // This field is read-only.
-  google.protobuf.StringValue search_term = 2;
+  google.protobuf.StringValue search_term = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The dynamically generated headline of the Dynamic Search Ad.
+  // Output only. The dynamically generated headline of the Dynamic Search Ad.
   //
   // This field is read-only.
-  google.protobuf.StringValue headline = 3;
+  google.protobuf.StringValue headline = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The dynamically selected landing page URL of the impression.
+  // Output only. The dynamically selected landing page URL of the impression.
   //
   // This field is read-only.
-  google.protobuf.StringValue landing_page = 4;
+  google.protobuf.StringValue landing_page = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The URL of page feed item served for the impression.
+  // Output only. The URL of page feed item served for the impression.
   //
   // This field is read-only.
-  google.protobuf.StringValue page_url = 5;
+  google.protobuf.StringValue page_url = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // True if query matches a negative keyword.
+  // Output only. True if query matches a negative keyword.
   //
   // This field is read-only.
-  google.protobuf.BoolValue has_negative_keyword = 6;
+  google.protobuf.BoolValue has_negative_keyword = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // True if query is added to targeted keywords.
+  // Output only. True if query is added to targeted keywords.
   //
   // This field is read-only.
-  google.protobuf.BoolValue has_matching_keyword = 7;
+  google.protobuf.BoolValue has_matching_keyword = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // True if query matches a negative url.
+  // Output only. True if query matches a negative url.
   //
   // This field is read-only.
-  google.protobuf.BoolValue has_negative_url = 8;
+  google.protobuf.BoolValue has_negative_url = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/expanded_landing_page_view.proto b/google/ads/googleads/v3/resources/expanded_landing_page_view.proto
index f8b2e4ff..c6402b15 100644
--- a/google/ads/googleads/v3/resources/expanded_landing_page_view.proto
+++ b/google/ads/googleads/v3/resources/expanded_landing_page_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,12 +40,17 @@ message ExpandedLandingPageView {
     pattern: "customers/{customer}/expandedLandingPageViews/{expanded_landing_page_view}"
   };
 
-  // The resource name of the expanded landing page view.
+  // Output only. The resource name of the expanded landing page view.
   // Expanded landing page view resource names have the form:
   //
   // `customers/{customer_id}/expandedLandingPageViews/{expanded_final_url_fingerprint}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ExpandedLandingPageView"
+    }
+  ];
 
-  // The final URL that clicks are directed to.
-  google.protobuf.StringValue expanded_final_url = 2;
+  // Output only. The final URL that clicks are directed to.
+  google.protobuf.StringValue expanded_final_url = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/extension_feed_item.proto b/google/ads/googleads/v3/resources/extension_feed_item.proto
index 3fa28177..5f834868 100644
--- a/google/ads/googleads/v3/resources/extension_feed_item.proto
+++ b/google/ads/googleads/v3/resources/extension_feed_item.proto
@@ -21,6 +21,7 @@ import "google/ads/googleads/v3/common/extensions.proto";
 import "google/ads/googleads/v3/enums/extension_type.proto";
 import "google/ads/googleads/v3/enums/feed_item_status.proto";
 import "google/ads/googleads/v3/enums/feed_item_target_device.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,18 +44,23 @@ message ExtensionFeedItem {
     pattern: "customers/{customer}/extensionFeedItems/{extension_feed_item}"
   };
 
-  // The resource name of the extension feed item.
+  // Immutable. The resource name of the extension feed item.
   // Extension feed item resource names have the form:
   //
   // `customers/{customer_id}/extensionFeedItems/{feed_item_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ExtensionFeedItem"
+    }
+  ];
 
-  // The ID of this feed item. Read-only.
-  google.protobuf.Int64Value id = 24;
+  // Output only. The ID of this feed item. Read-only.
+  google.protobuf.Int64Value id = 24 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The extension type of the extension feed item.
+  // Output only. The extension type of the extension feed item.
   // This field is read-only.
-  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 13;
+  google.ads.googleads.v3.enums.ExtensionTypeEnum.ExtensionType extension_type = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Start time in which this feed item is effective and can begin serving. The
   // time is in the customer's time zone.
@@ -77,14 +83,16 @@ message ExtensionFeedItem {
   google.ads.googleads.v3.enums.FeedItemTargetDeviceEnum.FeedItemTargetDevice device = 17;
 
   // The targeted geo target constant.
-  google.protobuf.StringValue targeted_geo_target_constant = 20;
+  google.protobuf.StringValue targeted_geo_target_constant = 20 [(google.api.resource_reference) = {
+                                                                   type: "googleads.googleapis.com/GeoTargetConstant"
+                                                                 }];
 
   // The targeted keyword.
   google.ads.googleads.v3.common.KeywordInfo targeted_keyword = 22;
 
-  // Status of the feed item.
+  // Output only. Status of the feed item.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedItemStatusEnum.FeedItemStatus status = 4;
+  google.ads.googleads.v3.enums.FeedItemStatusEnum.FeedItemStatus status = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Extension type.
   oneof extension {
@@ -112,14 +120,14 @@ message ExtensionFeedItem {
     // Promotion extension.
     google.ads.googleads.v3.common.PromotionFeedItem promotion_feed_item = 12;
 
-    // Location extension. Locations are synced from a GMB account into a feed.
+    // Output only. Location extension. Locations are synced from a GMB account into a feed.
     // This field is read-only.
-    google.ads.googleads.v3.common.LocationFeedItem location_feed_item = 14;
+    google.ads.googleads.v3.common.LocationFeedItem location_feed_item = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Affiliate location extension. Feed locations are populated by Google Ads
+    // Output only. Affiliate location extension. Feed locations are populated by Google Ads
     // based on a chain ID.
     // This field is read-only.
-    google.ads.googleads.v3.common.AffiliateLocationFeedItem affiliate_location_feed_item = 15;
+    google.ads.googleads.v3.common.AffiliateLocationFeedItem affiliate_location_feed_item = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
     // Hotel Callout extension.
     google.ads.googleads.v3.common.HotelCalloutFeedItem hotel_callout_feed_item = 23;
@@ -129,9 +137,13 @@ message ExtensionFeedItem {
   // a campaign or ad group will only serve with that resource.
   oneof serving_resource_targeting {
     // The targeted campaign.
-    google.protobuf.StringValue targeted_campaign = 18;
+    google.protobuf.StringValue targeted_campaign = 18 [(google.api.resource_reference) = {
+                                                          type: "googleads.googleapis.com/Campaign"
+                                                        }];
 
     // The targeted ad group.
-    google.protobuf.StringValue targeted_ad_group = 19;
+    google.protobuf.StringValue targeted_ad_group = 19 [(google.api.resource_reference) = {
+                                                          type: "googleads.googleapis.com/AdGroup"
+                                                        }];
   }
 }
diff --git a/google/ads/googleads/v3/resources/feed.proto b/google/ads/googleads/v3/resources/feed.proto
index d99ecd66..98c58d33 100644
--- a/google/ads/googleads/v3/resources/feed.proto
+++ b/google/ads/googleads/v3/resources/feed.proto
@@ -20,6 +20,7 @@ import "google/ads/googleads/v3/enums/affiliate_location_feed_relationship_type.
 import "google/ads/googleads/v3/enums/feed_attribute_type.proto";
 import "google/ads/googleads/v3/enums/feed_origin.proto";
 import "google/ads/googleads/v3/enums/feed_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -57,10 +58,10 @@ message Feed {
       google.protobuf.StringValue http_authorization_header = 3;
     }
 
-    // Required authentication token (from OAuth API) for the email.
+    // Immutable. Required authentication token (from OAuth API) for the email.
     // This field can only be specified in a create request. All its subfields
     // are not selectable.
-    OAuthInfo oauth_info = 1;
+    OAuthInfo oauth_info = 1 [(google.api.field_behavior) = IMMUTABLE];
 
     // Email address of a Google My Business account or email address of a
     // manager of the Google My Business account. Required.
@@ -101,18 +102,23 @@ message Feed {
     google.ads.googleads.v3.enums.AffiliateLocationFeedRelationshipTypeEnum.AffiliateLocationFeedRelationshipType relationship_type = 2;
   }
 
-  // The resource name of the feed.
+  // Immutable. The resource name of the feed.
   // Feed resource names have the form:
   //
   // `customers/{customer_id}/feeds/{feed_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // The ID of the feed.
+  // Output only. The ID of the feed.
   // This field is read-only.
-  google.protobuf.Int64Value id = 2;
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Name of the feed. Required.
-  google.protobuf.StringValue name = 3;
+  // Immutable. Name of the feed. Required.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = IMMUTABLE];
 
   // The Feed's attributes. Required on CREATE, unless
   // system_feed_generation_data is provided, in which case Google Ads will
@@ -124,12 +130,12 @@ message Feed {
   // be added, not removed.
   repeated FeedAttributeOperation attribute_operations = 9;
 
-  // Specifies who manages the FeedAttributes for the Feed.
-  google.ads.googleads.v3.enums.FeedOriginEnum.FeedOrigin origin = 5;
+  // Immutable. Specifies who manages the FeedAttributes for the Feed.
+  google.ads.googleads.v3.enums.FeedOriginEnum.FeedOrigin origin = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Status of the feed.
+  // Output only. Status of the feed.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedStatusEnum.FeedStatus status = 8;
+  google.ads.googleads.v3.enums.FeedStatusEnum.FeedStatus status = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The system data for the Feed. This data specifies information for
   // generating the feed items of the system generated feed.
@@ -179,9 +185,9 @@ message FeedAttributeOperation {
     ADD = 2;
   }
 
-  // Type of list operation to perform.
-  Operator operator = 1;
+  // Output only. Type of list operation to perform.
+  Operator operator = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The feed attribute being added to the list.
-  FeedAttribute value = 2;
+  // Output only. The feed attribute being added to the list.
+  FeedAttribute value = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/feed_item.proto b/google/ads/googleads/v3/resources/feed_item.proto
index 87bf3059..e683626f 100644
--- a/google/ads/googleads/v3/resources/feed_item.proto
+++ b/google/ads/googleads/v3/resources/feed_item.proto
@@ -28,6 +28,7 @@ import "google/ads/googleads/v3/enums/placeholder_type.proto";
 import "google/ads/googleads/v3/enums/policy_approval_status.proto";
 import "google/ads/googleads/v3/enums/policy_review_status.proto";
 import "google/ads/googleads/v3/errors/feed_item_validation_error.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -50,17 +51,27 @@ message FeedItem {
     pattern: "customers/{customer}/feedItems/{feed_item}"
   };
 
-  // The resource name of the feed item.
+  // Immutable. The resource name of the feed item.
   // Feed item resource names have the form:
   //
   // `customers/{customer_id}/feedItems/{feed_id}~{feed_item_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedItem"
+    }
+  ];
 
-  // The feed to which this feed item belongs.
-  google.protobuf.StringValue feed = 2;
+  // Immutable. The feed to which this feed item belongs.
+  google.protobuf.StringValue feed = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // The ID of this feed item.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of this feed item.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Start time in which this feed item is effective and can begin serving. The
   // time is in the customer's time zone.
@@ -85,17 +96,17 @@ message FeedItem {
   // `tracking_url_template`, `final_urls`, or `mobile_final_urls`.
   repeated google.ads.googleads.v3.common.CustomParameter url_custom_parameters = 8;
 
-  // Status of the feed item.
+  // Output only. Status of the feed item.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedItemStatusEnum.FeedItemStatus status = 9;
+  google.ads.googleads.v3.enums.FeedItemStatusEnum.FeedItemStatus status = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // List of info about a feed item's validation and approval state for active
+  // Output only. List of info about a feed item's validation and approval state for active
   // feed mappings. There will be an entry in the list for each type of feed
   // mapping associated with the feed, e.g. a feed with a sitelink and a call
   // feed mapping would cause every feed item associated with that feed to have
   // an entry in this list for both sitelink and call.
   // This field is read-only.
-  repeated FeedItemPlaceholderPolicyInfo policy_infos = 10;
+  repeated FeedItemPlaceholderPolicyInfo policy_infos = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // A feed item attribute value.
@@ -153,52 +164,52 @@ message FeedItemAttributeValue {
 // Policy, validation, and quality approval info for a feed item for the
 // specified placeholder type.
 message FeedItemPlaceholderPolicyInfo {
-  // The placeholder type.
-  google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type_enum = 10;
+  // Output only. The placeholder type.
+  google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type_enum = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The FeedMapping that contains the placeholder type.
-  google.protobuf.StringValue feed_mapping_resource_name = 2;
+  // Output only. The FeedMapping that contains the placeholder type.
+  google.protobuf.StringValue feed_mapping_resource_name = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Where the placeholder type is in the review process.
-  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 3;
+  // Output only. Where the placeholder type is in the review process.
+  google.ads.googleads.v3.enums.PolicyReviewStatusEnum.PolicyReviewStatus review_status = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The overall approval status of the placeholder type, calculated based on
+  // Output only. The overall approval status of the placeholder type, calculated based on
   // the status of its individual policy topic entries.
-  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 4;
+  google.ads.googleads.v3.enums.PolicyApprovalStatusEnum.PolicyApprovalStatus approval_status = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The list of policy findings for the placeholder type.
-  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 5;
+  // Output only. The list of policy findings for the placeholder type.
+  repeated google.ads.googleads.v3.common.PolicyTopicEntry policy_topic_entries = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The validation status of the palceholder type.
-  google.ads.googleads.v3.enums.FeedItemValidationStatusEnum.FeedItemValidationStatus validation_status = 6;
+  // Output only. The validation status of the palceholder type.
+  google.ads.googleads.v3.enums.FeedItemValidationStatusEnum.FeedItemValidationStatus validation_status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // List of placeholder type validation errors.
-  repeated FeedItemValidationError validation_errors = 7;
+  // Output only. List of placeholder type validation errors.
+  repeated FeedItemValidationError validation_errors = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Placeholder type quality evaluation approval status.
-  google.ads.googleads.v3.enums.FeedItemQualityApprovalStatusEnum.FeedItemQualityApprovalStatus quality_approval_status = 8;
+  // Output only. Placeholder type quality evaluation approval status.
+  google.ads.googleads.v3.enums.FeedItemQualityApprovalStatusEnum.FeedItemQualityApprovalStatus quality_approval_status = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // List of placeholder type quality evaluation disapproval reasons.
-  repeated google.ads.googleads.v3.enums.FeedItemQualityDisapprovalReasonEnum.FeedItemQualityDisapprovalReason quality_disapproval_reasons = 9;
+  // Output only. List of placeholder type quality evaluation disapproval reasons.
+  repeated google.ads.googleads.v3.enums.FeedItemQualityDisapprovalReasonEnum.FeedItemQualityDisapprovalReason quality_disapproval_reasons = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Stores a validation error and the set of offending feed attributes which
 // together are responsible for causing a feed item validation error.
 message FeedItemValidationError {
-  // Error code indicating what validation error was triggered. The description
+  // Output only. Error code indicating what validation error was triggered. The description
   // of the error can be found in the 'description' field.
-  google.ads.googleads.v3.errors.FeedItemValidationErrorEnum.FeedItemValidationError validation_error = 1;
+  google.ads.googleads.v3.errors.FeedItemValidationErrorEnum.FeedItemValidationError validation_error = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The description of the validation error.
-  google.protobuf.StringValue description = 2;
+  // Output only. The description of the validation error.
+  google.protobuf.StringValue description = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Set of feed attributes in the feed item flagged during validation. If
+  // Output only. Set of feed attributes in the feed item flagged during validation. If
   // empty, no specific feed attributes can be associated with the error
   // (e.g. error across the entire feed item).
-  repeated google.protobuf.Int64Value feed_attribute_ids = 3;
+  repeated google.protobuf.Int64Value feed_attribute_ids = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Any extra information related to this error which is not captured by
+  // Output only. Any extra information related to this error which is not captured by
   // validation_error and feed_attribute_id (e.g. placeholder field IDs when
   // feed_attribute_id is not mapped). Note that extra_info is not localized.
-  google.protobuf.StringValue extra_info = 5;
+  google.protobuf.StringValue extra_info = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/feed_item_target.proto b/google/ads/googleads/v3/resources/feed_item_target.proto
index 078419c3..d5ca398d 100644
--- a/google/ads/googleads/v3/resources/feed_item_target.proto
+++ b/google/ads/googleads/v3/resources/feed_item_target.proto
@@ -20,6 +20,7 @@ import "google/ads/googleads/v3/common/criteria.proto";
 import "google/ads/googleads/v3/enums/feed_item_target_device.proto";
 import "google/ads/googleads/v3/enums/feed_item_target_status.proto";
 import "google/ads/googleads/v3/enums/feed_item_target_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -42,42 +43,67 @@ message FeedItemTarget {
     pattern: "customers/{customer}/feedItemTargets/{feed_item_target}"
   };
 
-  // The resource name of the feed item target.
+  // Immutable. The resource name of the feed item target.
   // Feed item target resource names have the form:
   // `customers/{customer_id}/feedItemTargets/{feed_id}~{feed_item_id}~{feed_item_target_type}~{feed_item_target_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedItemTarget"
+    }
+  ];
 
-  // The feed item to which this feed item target belongs.
-  google.protobuf.StringValue feed_item = 2;
+  // Immutable. The feed item to which this feed item target belongs.
+  google.protobuf.StringValue feed_item = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedItem"
+    }
+  ];
 
-  // The target type of this feed item target. This field is read-only.
-  google.ads.googleads.v3.enums.FeedItemTargetTypeEnum.FeedItemTargetType feed_item_target_type = 3;
+  // Output only. The target type of this feed item target. This field is read-only.
+  google.ads.googleads.v3.enums.FeedItemTargetTypeEnum.FeedItemTargetType feed_item_target_type = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ID of the targeted resource. This field is read-only.
-  google.protobuf.Int64Value feed_item_target_id = 6;
+  // Output only. The ID of the targeted resource. This field is read-only.
+  google.protobuf.Int64Value feed_item_target_id = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Status of the feed item target.
+  // Output only. Status of the feed item target.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedItemTargetStatusEnum.FeedItemTargetStatus status = 11;
+  google.ads.googleads.v3.enums.FeedItemTargetStatusEnum.FeedItemTargetStatus status = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The targeted resource.
   oneof target {
-    // The targeted campaign.
-    google.protobuf.StringValue campaign = 4;
+    // Immutable. The targeted campaign.
+    google.protobuf.StringValue campaign = 4 [
+      (google.api.field_behavior) = IMMUTABLE,
+      (google.api.resource_reference) = {
+        type: "googleads.googleapis.com/Campaign"
+      }
+    ];
 
-    // The targeted ad group.
-    google.protobuf.StringValue ad_group = 5;
+    // Immutable. The targeted ad group.
+    google.protobuf.StringValue ad_group = 5 [
+      (google.api.field_behavior) = IMMUTABLE,
+      (google.api.resource_reference) = {
+        type: "googleads.googleapis.com/AdGroup"
+      }
+    ];
 
-    // The targeted keyword.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 7;
+    // Immutable. The targeted keyword.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The targeted geo target constant resource name.
-    google.protobuf.StringValue geo_target_constant = 8;
+    // Immutable. The targeted geo target constant resource name.
+    google.protobuf.StringValue geo_target_constant = 8 [
+      (google.api.field_behavior) = IMMUTABLE,
+      (google.api.resource_reference) = {
+        type: "googleads.googleapis.com/GeoTargetConstant"
+      }
+    ];
 
-    // The targeted device.
-    google.ads.googleads.v3.enums.FeedItemTargetDeviceEnum.FeedItemTargetDevice device = 9;
+    // Immutable. The targeted device.
+    google.ads.googleads.v3.enums.FeedItemTargetDeviceEnum.FeedItemTargetDevice device = 9 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The targeted schedule.
-    google.ads.googleads.v3.common.AdScheduleInfo ad_schedule = 10;
+    // Immutable. The targeted schedule.
+    google.ads.googleads.v3.common.AdScheduleInfo ad_schedule = 10 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/feed_mapping.proto b/google/ads/googleads/v3/resources/feed_mapping.proto
index bf54b944..b0a0d51b 100644
--- a/google/ads/googleads/v3/resources/feed_mapping.proto
+++ b/google/ads/googleads/v3/resources/feed_mapping.proto
@@ -40,6 +40,7 @@ import "google/ads/googleads/v3/enums/real_estate_placeholder_field.proto";
 import "google/ads/googleads/v3/enums/sitelink_placeholder_field.proto";
 import "google/ads/googleads/v3/enums/structured_snippet_placeholder_field.proto";
 import "google/ads/googleads/v3/enums/travel_placeholder_field.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -62,114 +63,124 @@ message FeedMapping {
     pattern: "customers/{customer}/feedMappings/{feed_mapping}"
   };
 
-  // The resource name of the feed mapping.
+  // Immutable. The resource name of the feed mapping.
   // Feed mapping resource names have the form:
   //
   // `customers/{customer_id}/feedMappings/{feed_id}~{feed_mapping_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedMapping"
+    }
+  ];
 
-  // The feed of this feed mapping.
-  google.protobuf.StringValue feed = 2;
+  // Immutable. The feed of this feed mapping.
+  google.protobuf.StringValue feed = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Feed"
+    }
+  ];
 
-  // Feed attributes to field mappings. These mappings are a one-to-many
+  // Immutable. Feed attributes to field mappings. These mappings are a one-to-many
   // relationship meaning that 1 feed attribute can be used to populate
   // multiple placeholder fields, but 1 placeholder field can only draw
   // data from 1 feed attribute. Ad Customizer is an exception, 1 placeholder
   // field can be mapped to multiple feed attributes. Required.
-  repeated AttributeFieldMapping attribute_field_mappings = 5;
+  repeated AttributeFieldMapping attribute_field_mappings = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // Status of the feed mapping.
+  // Output only. Status of the feed mapping.
   // This field is read-only.
-  google.ads.googleads.v3.enums.FeedMappingStatusEnum.FeedMappingStatus status = 6;
+  google.ads.googleads.v3.enums.FeedMappingStatusEnum.FeedMappingStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Feed mapping target. Can be either a placeholder or a criterion. For a
   // given feed, the active FeedMappings must have unique targets. Required.
   oneof target {
-    // The placeholder type of this mapping (i.e., if the mapping maps feed
+    // Immutable. The placeholder type of this mapping (i.e., if the mapping maps feed
     // attributes to placeholder fields).
-    google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type = 3;
+    google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-    // The criterion type of this mapping (i.e., if the mapping maps feed
+    // Immutable. The criterion type of this mapping (i.e., if the mapping maps feed
     // attributes to criterion fields).
-    google.ads.googleads.v3.enums.FeedMappingCriterionTypeEnum.FeedMappingCriterionType criterion_type = 4;
+    google.ads.googleads.v3.enums.FeedMappingCriterionTypeEnum.FeedMappingCriterionType criterion_type = 4 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
 
 // Maps from feed attribute id to a placeholder or criterion field id.
 message AttributeFieldMapping {
-  // Feed attribute from which to map.
-  google.protobuf.Int64Value feed_attribute_id = 1;
+  // Immutable. Feed attribute from which to map.
+  google.protobuf.Int64Value feed_attribute_id = 1 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The placeholder field ID. If a placeholder field enum is not published in
+  // Output only. The placeholder field ID. If a placeholder field enum is not published in
   // the current API version, then this field will be populated and the field
   // oneof will be empty.
   // This field is read-only.
-  google.protobuf.Int64Value field_id = 2;
+  google.protobuf.Int64Value field_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Placeholder or criterion field to be populated using data from
   // the above feed attribute. Required.
   oneof field {
-    // Sitelink Placeholder Fields.
-    google.ads.googleads.v3.enums.SitelinkPlaceholderFieldEnum.SitelinkPlaceholderField sitelink_field = 3;
+    // Immutable. Sitelink Placeholder Fields.
+    google.ads.googleads.v3.enums.SitelinkPlaceholderFieldEnum.SitelinkPlaceholderField sitelink_field = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Call Placeholder Fields.
-    google.ads.googleads.v3.enums.CallPlaceholderFieldEnum.CallPlaceholderField call_field = 4;
+    // Immutable. Call Placeholder Fields.
+    google.ads.googleads.v3.enums.CallPlaceholderFieldEnum.CallPlaceholderField call_field = 4 [(google.api.field_behavior) = IMMUTABLE];
 
-    // App Placeholder Fields.
-    google.ads.googleads.v3.enums.AppPlaceholderFieldEnum.AppPlaceholderField app_field = 5;
+    // Immutable. App Placeholder Fields.
+    google.ads.googleads.v3.enums.AppPlaceholderFieldEnum.AppPlaceholderField app_field = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Location Placeholder Fields. This field is read-only.
-    google.ads.googleads.v3.enums.LocationPlaceholderFieldEnum.LocationPlaceholderField location_field = 6;
+    // Output only. Location Placeholder Fields. This field is read-only.
+    google.ads.googleads.v3.enums.LocationPlaceholderFieldEnum.LocationPlaceholderField location_field = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Affiliate Location Placeholder Fields. This field is read-only.
-    google.ads.googleads.v3.enums.AffiliateLocationPlaceholderFieldEnum.AffiliateLocationPlaceholderField affiliate_location_field = 7;
+    // Output only. Affiliate Location Placeholder Fields. This field is read-only.
+    google.ads.googleads.v3.enums.AffiliateLocationPlaceholderFieldEnum.AffiliateLocationPlaceholderField affiliate_location_field = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Callout Placeholder Fields.
-    google.ads.googleads.v3.enums.CalloutPlaceholderFieldEnum.CalloutPlaceholderField callout_field = 8;
+    // Immutable. Callout Placeholder Fields.
+    google.ads.googleads.v3.enums.CalloutPlaceholderFieldEnum.CalloutPlaceholderField callout_field = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Structured Snippet Placeholder Fields.
-    google.ads.googleads.v3.enums.StructuredSnippetPlaceholderFieldEnum.StructuredSnippetPlaceholderField structured_snippet_field = 9;
+    // Immutable. Structured Snippet Placeholder Fields.
+    google.ads.googleads.v3.enums.StructuredSnippetPlaceholderFieldEnum.StructuredSnippetPlaceholderField structured_snippet_field = 9 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Message Placeholder Fields.
-    google.ads.googleads.v3.enums.MessagePlaceholderFieldEnum.MessagePlaceholderField message_field = 10;
+    // Immutable. Message Placeholder Fields.
+    google.ads.googleads.v3.enums.MessagePlaceholderFieldEnum.MessagePlaceholderField message_field = 10 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Price Placeholder Fields.
-    google.ads.googleads.v3.enums.PricePlaceholderFieldEnum.PricePlaceholderField price_field = 11;
+    // Immutable. Price Placeholder Fields.
+    google.ads.googleads.v3.enums.PricePlaceholderFieldEnum.PricePlaceholderField price_field = 11 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Promotion Placeholder Fields.
-    google.ads.googleads.v3.enums.PromotionPlaceholderFieldEnum.PromotionPlaceholderField promotion_field = 12;
+    // Immutable. Promotion Placeholder Fields.
+    google.ads.googleads.v3.enums.PromotionPlaceholderFieldEnum.PromotionPlaceholderField promotion_field = 12 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Ad Customizer Placeholder Fields
-    google.ads.googleads.v3.enums.AdCustomizerPlaceholderFieldEnum.AdCustomizerPlaceholderField ad_customizer_field = 13;
+    // Immutable. Ad Customizer Placeholder Fields
+    google.ads.googleads.v3.enums.AdCustomizerPlaceholderFieldEnum.AdCustomizerPlaceholderField ad_customizer_field = 13 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Dynamic Search Ad Page Feed Fields.
-    google.ads.googleads.v3.enums.DsaPageFeedCriterionFieldEnum.DsaPageFeedCriterionField dsa_page_feed_field = 14;
+    // Immutable. Dynamic Search Ad Page Feed Fields.
+    google.ads.googleads.v3.enums.DsaPageFeedCriterionFieldEnum.DsaPageFeedCriterionField dsa_page_feed_field = 14 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Location Target Fields.
-    google.ads.googleads.v3.enums.LocationExtensionTargetingCriterionFieldEnum.LocationExtensionTargetingCriterionField location_extension_targeting_field = 15;
+    // Immutable. Location Target Fields.
+    google.ads.googleads.v3.enums.LocationExtensionTargetingCriterionFieldEnum.LocationExtensionTargetingCriterionField location_extension_targeting_field = 15 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Education Placeholder Fields
-    google.ads.googleads.v3.enums.EducationPlaceholderFieldEnum.EducationPlaceholderField education_field = 16;
+    // Immutable. Education Placeholder Fields
+    google.ads.googleads.v3.enums.EducationPlaceholderFieldEnum.EducationPlaceholderField education_field = 16 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Flight Placeholder Fields
-    google.ads.googleads.v3.enums.FlightPlaceholderFieldEnum.FlightPlaceholderField flight_field = 17;
+    // Immutable. Flight Placeholder Fields
+    google.ads.googleads.v3.enums.FlightPlaceholderFieldEnum.FlightPlaceholderField flight_field = 17 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Custom Placeholder Fields
-    google.ads.googleads.v3.enums.CustomPlaceholderFieldEnum.CustomPlaceholderField custom_field = 18;
+    // Immutable. Custom Placeholder Fields
+    google.ads.googleads.v3.enums.CustomPlaceholderFieldEnum.CustomPlaceholderField custom_field = 18 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Hotel Placeholder Fields
-    google.ads.googleads.v3.enums.HotelPlaceholderFieldEnum.HotelPlaceholderField hotel_field = 19;
+    // Immutable. Hotel Placeholder Fields
+    google.ads.googleads.v3.enums.HotelPlaceholderFieldEnum.HotelPlaceholderField hotel_field = 19 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Real Estate Placeholder Fields
-    google.ads.googleads.v3.enums.RealEstatePlaceholderFieldEnum.RealEstatePlaceholderField real_estate_field = 20;
+    // Immutable. Real Estate Placeholder Fields
+    google.ads.googleads.v3.enums.RealEstatePlaceholderFieldEnum.RealEstatePlaceholderField real_estate_field = 20 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Travel Placeholder Fields
-    google.ads.googleads.v3.enums.TravelPlaceholderFieldEnum.TravelPlaceholderField travel_field = 21;
+    // Immutable. Travel Placeholder Fields
+    google.ads.googleads.v3.enums.TravelPlaceholderFieldEnum.TravelPlaceholderField travel_field = 21 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Local Placeholder Fields
-    google.ads.googleads.v3.enums.LocalPlaceholderFieldEnum.LocalPlaceholderField local_field = 22;
+    // Immutable. Local Placeholder Fields
+    google.ads.googleads.v3.enums.LocalPlaceholderFieldEnum.LocalPlaceholderField local_field = 22 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Job Placeholder Fields
-    google.ads.googleads.v3.enums.JobPlaceholderFieldEnum.JobPlaceholderField job_field = 23;
+    // Immutable. Job Placeholder Fields
+    google.ads.googleads.v3.enums.JobPlaceholderFieldEnum.JobPlaceholderField job_field = 23 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/feed_placeholder_view.proto b/google/ads/googleads/v3/resources/feed_placeholder_view.proto
index 9cbe553e..1857fb14 100644
--- a/google/ads/googleads/v3/resources/feed_placeholder_view.proto
+++ b/google/ads/googleads/v3/resources/feed_placeholder_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/placeholder_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -38,12 +39,17 @@ message FeedPlaceholderView {
     pattern: "customers/{customer}/feedPlaceholderViews/{feed_placeholder_view}"
   };
 
-  // The resource name of the feed placeholder view.
+  // Output only. The resource name of the feed placeholder view.
   // Feed placeholder view resource names have the form:
   //
   // `customers/{customer_id}/feedPlaceholderViews/{placeholder_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/FeedPlaceholderView"
+    }
+  ];
 
-  // The placeholder type of the feed placeholder view.
-  google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type = 2;
+  // Output only. The placeholder type of the feed placeholder view.
+  google.ads.googleads.v3.enums.PlaceholderTypeEnum.PlaceholderType placeholder_type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/gender_view.proto b/google/ads/googleads/v3/resources/gender_view.proto
index 473a5342..ab28a236 100644
--- a/google/ads/googleads/v3/resources/gender_view.proto
+++ b/google/ads/googleads/v3/resources/gender_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message GenderView {
     pattern: "customers/{customer}/genderViews/{gender_view}"
   };
 
-  // The resource name of the gender view.
+  // Output only. The resource name of the gender view.
   // Gender view resource names have the form:
   //
   // `customers/{customer_id}/genderViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/GenderView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/geo_target_constant.proto b/google/ads/googleads/v3/resources/geo_target_constant.proto
index 47806522..ca8e916f 100644
--- a/google/ads/googleads/v3/resources/geo_target_constant.proto
+++ b/google/ads/googleads/v3/resources/geo_target_constant.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/geo_target_constant_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,28 +40,33 @@ message GeoTargetConstant {
     pattern: "geoTargetConstants/{geo_target_constant}"
   };
 
-  // The resource name of the geo target constant.
+  // Output only. The resource name of the geo target constant.
   // Geo target constant resource names have the form:
   //
   // `geoTargetConstants/{geo_target_constant_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/GeoTargetConstant"
+    }
+  ];
 
-  // The ID of the geo target constant.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the geo target constant.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Geo target constant English name.
-  google.protobuf.StringValue name = 4;
+  // Output only. Geo target constant English name.
+  google.protobuf.StringValue name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ISO-3166-1 alpha-2 country code that is associated with the target.
-  google.protobuf.StringValue country_code = 5;
+  // Output only. The ISO-3166-1 alpha-2 country code that is associated with the target.
+  google.protobuf.StringValue country_code = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Geo target constant target type.
-  google.protobuf.StringValue target_type = 6;
+  // Output only. Geo target constant target type.
+  google.protobuf.StringValue target_type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Geo target constant status.
-  google.ads.googleads.v3.enums.GeoTargetConstantStatusEnum.GeoTargetConstantStatus status = 7;
+  // Output only. Geo target constant status.
+  google.ads.googleads.v3.enums.GeoTargetConstantStatusEnum.GeoTargetConstantStatus status = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The fully qualified English name, consisting of the target's name and that
+  // Output only. The fully qualified English name, consisting of the target's name and that
   // of its parent and country.
-  google.protobuf.StringValue canonical_name = 8;
+  google.protobuf.StringValue canonical_name = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/geographic_view.proto b/google/ads/googleads/v3/resources/geographic_view.proto
index 01621405..39b36371 100644
--- a/google/ads/googleads/v3/resources/geographic_view.proto
+++ b/google/ads/googleads/v3/resources/geographic_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/geo_targeting_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -44,15 +45,20 @@ message GeographicView {
     pattern: "customers/{customer}/geographicViews/{geographic_view}"
   };
 
-  // The resource name of the geographic view.
+  // Output only. The resource name of the geographic view.
   // Geographic view resource names have the form:
   //
   // `customers/{customer_id}/geographicViews/{country_criterion_id}~{location_type}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/GeographicView"
+    }
+  ];
 
-  // Type of the geo targeting of the campaign.
-  google.ads.googleads.v3.enums.GeoTargetingTypeEnum.GeoTargetingType location_type = 3;
+  // Output only. Type of the geo targeting of the campaign.
+  google.ads.googleads.v3.enums.GeoTargetingTypeEnum.GeoTargetingType location_type = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Criterion Id for the country.
-  google.protobuf.Int64Value country_criterion_id = 4;
+  // Output only. Criterion Id for the country.
+  google.protobuf.Int64Value country_criterion_id = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/google_ads_field.proto b/google/ads/googleads/v3/resources/google_ads_field.proto
index 02f8d45a..3dc08c1f 100644
--- a/google/ads/googleads/v3/resources/google_ads_field.proto
+++ b/google/ads/googleads/v3/resources/google_ads_field.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/google_ads_field_category.proto";
 import "google/ads/googleads/v3/enums/google_ads_field_data_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,51 +41,56 @@ message GoogleAdsField {
     pattern: "googleAdsFields/{google_ads_field}"
   };
 
-  // The resource name of the artifact.
+  // Output only. The resource name of the artifact.
   // Artifact resource names have the form:
   //
   // `googleAdsFields/{name}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/GoogleAdsField"
+    }
+  ];
 
-  // The name of the artifact.
-  google.protobuf.StringValue name = 2;
+  // Output only. The name of the artifact.
+  google.protobuf.StringValue name = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The category of the artifact.
-  google.ads.googleads.v3.enums.GoogleAdsFieldCategoryEnum.GoogleAdsFieldCategory category = 3;
+  // Output only. The category of the artifact.
+  google.ads.googleads.v3.enums.GoogleAdsFieldCategoryEnum.GoogleAdsFieldCategory category = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the artifact can be used in a SELECT clause in search
+  // Output only. Whether the artifact can be used in a SELECT clause in search
   // queries.
-  google.protobuf.BoolValue selectable = 4;
+  google.protobuf.BoolValue selectable = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the artifact can be used in a WHERE clause in search
+  // Output only. Whether the artifact can be used in a WHERE clause in search
   // queries.
-  google.protobuf.BoolValue filterable = 5;
+  google.protobuf.BoolValue filterable = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the artifact can be used in a ORDER BY clause in search
+  // Output only. Whether the artifact can be used in a ORDER BY clause in search
   // queries.
-  google.protobuf.BoolValue sortable = 6;
+  google.protobuf.BoolValue sortable = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The names of all resources, segments, and metrics that are selectable with
+  // Output only. The names of all resources, segments, and metrics that are selectable with
   // the described artifact.
-  repeated google.protobuf.StringValue selectable_with = 7;
+  repeated google.protobuf.StringValue selectable_with = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The names of all resources that are selectable with the described
+  // Output only. The names of all resources that are selectable with the described
   // artifact. Fields from these resources do not segment metrics when included
   // in search queries.
   //
   // This field is only set for artifacts whose category is RESOURCE.
-  repeated google.protobuf.StringValue attribute_resources = 8;
+  repeated google.protobuf.StringValue attribute_resources = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // At and beyond version V1 this field lists the names of all metrics that are
+  // Output only. At and beyond version V1 this field lists the names of all metrics that are
   // selectable with the described artifact when it is used in the FROM clause.
   // It is only set for artifacts whose category is RESOURCE.
   //
   // Before version V1 this field lists the names of all metrics that are
   // selectable with the described artifact. It is only set for artifacts whose
   // category is either RESOURCE or SEGMENT
-  repeated google.protobuf.StringValue metrics = 9;
+  repeated google.protobuf.StringValue metrics = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // At and beyond version V1 this field lists the names of all artifacts,
+  // Output only. At and beyond version V1 this field lists the names of all artifacts,
   // whether a segment or another resource, that segment metrics when included
   // in search queries and when the described artifact is used in the FROM
   // clause. It is only set for artifacts whose category is RESOURCE.
@@ -93,20 +99,20 @@ message GoogleAdsField {
   // segment or another resource, that segment metrics when included in search
   // queries. It is only set for artifacts of category RESOURCE, SEGMENT or
   // METRIC.
-  repeated google.protobuf.StringValue segments = 10;
+  repeated google.protobuf.StringValue segments = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Values the artifact can assume if it is a field of type ENUM.
+  // Output only. Values the artifact can assume if it is a field of type ENUM.
   //
   // This field is only set for artifacts of category SEGMENT or ATTRIBUTE.
-  repeated google.protobuf.StringValue enum_values = 11;
+  repeated google.protobuf.StringValue enum_values = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // This field determines the operators that can be used with the artifact
+  // Output only. This field determines the operators that can be used with the artifact
   // in WHERE clauses.
-  google.ads.googleads.v3.enums.GoogleAdsFieldDataTypeEnum.GoogleAdsFieldDataType data_type = 12;
+  google.ads.googleads.v3.enums.GoogleAdsFieldDataTypeEnum.GoogleAdsFieldDataType data_type = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The URL of proto describing the artifact's data type.
-  google.protobuf.StringValue type_url = 13;
+  // Output only. The URL of proto describing the artifact's data type.
+  google.protobuf.StringValue type_url = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the field artifact is repeated.
-  google.protobuf.BoolValue is_repeated = 14;
+  // Output only. Whether the field artifact is repeated.
+  google.protobuf.BoolValue is_repeated = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/group_placement_view.proto b/google/ads/googleads/v3/resources/group_placement_view.proto
index d1d1c9c5..78e5152e 100644
--- a/google/ads/googleads/v3/resources/group_placement_view.proto
+++ b/google/ads/googleads/v3/resources/group_placement_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/placement_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,23 +40,28 @@ message GroupPlacementView {
     pattern: "customers/{customer}/groupPlacementViews/{group_placement_view}"
   };
 
-  // The resource name of the group placement view.
+  // Output only. The resource name of the group placement view.
   // Group placement view resource names have the form:
   //
   // `customers/{customer_id}/groupPlacementViews/{ad_group_id}~{base64_placement}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/GroupPlacementView"
+    }
+  ];
 
-  // The automatic placement string at group level, e. g. web domain, mobile
+  // Output only. The automatic placement string at group level, e. g. web domain, mobile
   // app ID, or a YouTube channel ID.
-  google.protobuf.StringValue placement = 2;
+  google.protobuf.StringValue placement = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Domain name for websites and YouTube channel name for YouTube channels.
-  google.protobuf.StringValue display_name = 3;
+  // Output only. Domain name for websites and YouTube channel name for YouTube channels.
+  google.protobuf.StringValue display_name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // URL of the group placement, e.g. domain, link to the mobile application in
+  // Output only. URL of the group placement, e.g. domain, link to the mobile application in
   // app store, or a YouTube channel URL.
-  google.protobuf.StringValue target_url = 4;
+  google.protobuf.StringValue target_url = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Type of the placement, e.g. Website, YouTube Channel, Mobile Application.
-  google.ads.googleads.v3.enums.PlacementTypeEnum.PlacementType placement_type = 5;
+  // Output only. Type of the placement, e.g. Website, YouTube Channel, Mobile Application.
+  google.ads.googleads.v3.enums.PlacementTypeEnum.PlacementType placement_type = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/hotel_group_view.proto b/google/ads/googleads/v3/resources/hotel_group_view.proto
index e082f72e..5eaf7a22 100644
--- a/google/ads/googleads/v3/resources/hotel_group_view.proto
+++ b/google/ads/googleads/v3/resources/hotel_group_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message HotelGroupView {
     pattern: "customers/{customer}/hotelGroupViews/{hotel_group_view}"
   };
 
-  // The resource name of the hotel group view.
+  // Output only. The resource name of the hotel group view.
   // Hotel Group view resource names have the form:
   //
   // `customers/{customer_id}/hotelGroupViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/HotelGroupView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/hotel_performance_view.proto b/google/ads/googleads/v3/resources/hotel_performance_view.proto
index cadbdd9e..8af34991 100644
--- a/google/ads/googleads/v3/resources/hotel_performance_view.proto
+++ b/google/ads/googleads/v3/resources/hotel_performance_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message HotelPerformanceView {
     pattern: "customers/{customer}/hotelPerformanceView"
   };
 
-  // The resource name of the hotel performance view.
+  // Output only. The resource name of the hotel performance view.
   // Hotel performance view resource names have the form:
   //
   // `customers/{customer_id}/hotelPerformanceView`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/HotelPerformanceView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/invoice.proto b/google/ads/googleads/v3/resources/invoice.proto
index c43a7775..1e86c822 100644
--- a/google/ads/googleads/v3/resources/invoice.proto
+++ b/google/ads/googleads/v3/resources/invoice.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/dates.proto";
 import "google/ads/googleads/v3/enums/invoice_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -44,121 +45,126 @@ message Invoice {
 
   // Represents a summarized account budget billable cost.
   message AccountBudgetSummary {
-    // The resource name of the customer associated with this account budget.
+    // Output only. The resource name of the customer associated with this account budget.
     // This contains the customer ID, which appears on the invoice PDF as
     // "Account ID".
     // Customer resource names have the form:
     //
     // `customers/{customer_id}`
-    google.protobuf.StringValue customer = 1;
+    google.protobuf.StringValue customer = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The descriptive name of the account budget’s customer. It appears on the
+    // Output only. The descriptive name of the account budget’s customer. It appears on the
     // invoice PDF as "Account".
-    google.protobuf.StringValue customer_descriptive_name = 2;
+    google.protobuf.StringValue customer_descriptive_name = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The resource name of the account budget associated with this summarized
+    // Output only. The resource name of the account budget associated with this summarized
     // billable cost.
     // AccountBudget resource names have the form:
     //
     // `customers/{customer_id}/accountBudgets/{account_budget_id}`
-    google.protobuf.StringValue account_budget = 3;
+    google.protobuf.StringValue account_budget = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The name of the account budget. It appears on the invoice PDF as "Account
+    // Output only. The name of the account budget. It appears on the invoice PDF as "Account
     // budget".
-    google.protobuf.StringValue account_budget_name = 4;
+    google.protobuf.StringValue account_budget_name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The purchase order number of the account budget. It appears on the
+    // Output only. The purchase order number of the account budget. It appears on the
     // invoice PDF as "Purchase order".
-    google.protobuf.StringValue purchase_order_number = 5;
+    google.protobuf.StringValue purchase_order_number = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The pretax subtotal amount attributable to this budget during the service
+    // Output only. The pretax subtotal amount attributable to this budget during the service
     // period, in micros.
-    google.protobuf.Int64Value subtotal_amount_micros = 6;
+    google.protobuf.Int64Value subtotal_amount_micros = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The tax amount attributable to this budget during the service period, in
+    // Output only. The tax amount attributable to this budget during the service period, in
     // micros.
-    google.protobuf.Int64Value tax_amount_micros = 7;
+    google.protobuf.Int64Value tax_amount_micros = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The total amount attributable to this budget during the service period,
+    // Output only. The total amount attributable to this budget during the service period,
     // in micros. This equals the sum of the account budget subtotal amount and
     // the account budget tax amount.
-    google.protobuf.Int64Value total_amount_micros = 8;
+    google.protobuf.Int64Value total_amount_micros = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The billable activity date range of the account budget, within the
+    // Output only. The billable activity date range of the account budget, within the
     // service date range of this invoice. The end date is inclusive. This can
     // be different from the account budget's start and end time.
-    google.ads.googleads.v3.common.DateRange billable_activity_date_range = 9;
+    google.ads.googleads.v3.common.DateRange billable_activity_date_range = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The resource name of the invoice. Multiple customers can share a given
+  // Output only. The resource name of the invoice. Multiple customers can share a given
   // invoice, so multiple resource names may point to the same invoice.
   // Invoice resource names have the form:
   //
   // `customers/{customer_id}/invoices/{invoice_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Invoice"
+    }
+  ];
 
-  // The ID of the invoice. It appears on the invoice PDF as "Invoice number".
-  google.protobuf.StringValue id = 2;
+  // Output only. The ID of the invoice. It appears on the invoice PDF as "Invoice number".
+  google.protobuf.StringValue id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of invoice.
-  google.ads.googleads.v3.enums.InvoiceTypeEnum.InvoiceType type = 3;
+  // Output only. The type of invoice.
+  google.ads.googleads.v3.enums.InvoiceTypeEnum.InvoiceType type = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of this invoice’s billing setup.
+  // Output only. The resource name of this invoice’s billing setup.
   //
   // `customers/{customer_id}/billingSetups/{billing_setup_id}`
-  google.protobuf.StringValue billing_setup = 4;
+  google.protobuf.StringValue billing_setup = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A 16 digit ID used to identify the payments account associated with the
+  // Output only. A 16 digit ID used to identify the payments account associated with the
   // billing setup, e.g. "1234-5678-9012-3456". It appears on the invoice PDF as
   // "Billing Account Number".
-  google.protobuf.StringValue payments_account_id = 5;
+  google.protobuf.StringValue payments_account_id = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A 12 digit ID used to identify the payments profile associated with the
+  // Output only. A 12 digit ID used to identify the payments profile associated with the
   // billing setup, e.g. "1234-5678-9012". It appears on the invoice PDF as
   // "Billing ID".
-  google.protobuf.StringValue payments_profile_id = 6;
+  google.protobuf.StringValue payments_profile_id = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The issue date in yyyy-mm-dd format. It appears on the invoice PDF as
+  // Output only. The issue date in yyyy-mm-dd format. It appears on the invoice PDF as
   // either "Issue date" or "Invoice date".
-  google.protobuf.StringValue issue_date = 7;
+  google.protobuf.StringValue issue_date = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The due date in yyyy-mm-dd format.
-  google.protobuf.StringValue due_date = 8;
+  // Output only. The due date in yyyy-mm-dd format.
+  google.protobuf.StringValue due_date = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The service period date range of this invoice. The end date is inclusive.
-  google.ads.googleads.v3.common.DateRange service_date_range = 9;
+  // Output only. The service period date range of this invoice. The end date is inclusive.
+  google.ads.googleads.v3.common.DateRange service_date_range = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The currency code. All costs are returned in this currency. A subset of the
+  // Output only. The currency code. All costs are returned in this currency. A subset of the
   // currency codes derived from the ISO 4217 standard is supported.
-  google.protobuf.StringValue currency_code = 10;
+  google.protobuf.StringValue currency_code = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The total amount of invoice level adjustments. These adjustments are made
+  // Output only. The total amount of invoice level adjustments. These adjustments are made
   // on the invoice, not on a specific account budget.
-  google.protobuf.Int64Value invoice_level_adjustments_micros = 11;
+  google.protobuf.Int64Value invoice_level_adjustments_micros = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The pretax subtotal amount, in micros. This equals the sum of the
+  // Output only. The pretax subtotal amount, in micros. This equals the sum of the
   // AccountBudgetSummary subtotal amounts, plus the invoice level adjustments.
-  google.protobuf.Int64Value subtotal_amount_micros = 12;
+  google.protobuf.Int64Value subtotal_amount_micros = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The sum of all taxes on the invoice, in micros. This equals the sum of the
+  // Output only. The sum of all taxes on the invoice, in micros. This equals the sum of the
   // AccountBudgetSummary tax amounts, plus taxes not associated with a specific
   // account budget.
-  google.protobuf.Int64Value tax_amount_micros = 13;
+  google.protobuf.Int64Value tax_amount_micros = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The total amount, in micros. This equals the sum of the invoice subtotal
+  // Output only. The total amount, in micros. This equals the sum of the invoice subtotal
   // amount and the invoice tax amount.
-  google.protobuf.Int64Value total_amount_micros = 14;
+  google.protobuf.Int64Value total_amount_micros = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the original invoice corrected, wrote off, or canceled
+  // Output only. The resource name of the original invoice corrected, wrote off, or canceled
   // by this invoice, if applicable. If `corrected_invoice` is set,
   // `replaced_invoices` will not be set.
   //
   // Invoice resource names have the form:
   //
   // `customers/{customer_id}/invoices/{invoice_id}`
-  google.protobuf.StringValue corrected_invoice = 15;
+  google.protobuf.StringValue corrected_invoice = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the original invoice(s) being rebilled or replaced by
+  // Output only. The resource name of the original invoice(s) being rebilled or replaced by
   // this invoice, if applicable. There might be multiple replaced invoices due
   // to invoice consolidation. The replaced invoices may not belong to the same
   // payments account. If `replaced_invoices` is set, `corrected_invoice` will
@@ -166,13 +172,13 @@ message Invoice {
   // Invoice resource names have the form:
   //
   // `customers/{customer_id}/invoices/{invoice_id}`
-  repeated google.protobuf.StringValue replaced_invoices = 16;
+  repeated google.protobuf.StringValue replaced_invoices = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The URL to a PDF copy of the invoice. Users need to pass in their OAuth
+  // Output only. The URL to a PDF copy of the invoice. Users need to pass in their OAuth
   // token to request the PDF with this URL.
-  google.protobuf.StringValue pdf_url = 17;
+  google.protobuf.StringValue pdf_url = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The list of summarized account budget information associated with this
+  // Output only. The list of summarized account budget information associated with this
   // invoice.
-  repeated AccountBudgetSummary account_budget_summaries = 18;
+  repeated AccountBudgetSummary account_budget_summaries = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/keyword_plan.proto b/google/ads/googleads/v3/resources/keyword_plan.proto
index 6cfc59f0..58e8b8c8 100644
--- a/google/ads/googleads/v3/resources/keyword_plan.proto
+++ b/google/ads/googleads/v3/resources/keyword_plan.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/dates.proto";
 import "google/ads/googleads/v3/enums/keyword_plan_forecast_interval.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -42,14 +43,19 @@ message KeywordPlan {
     pattern: "customers/{customer}/keywordPlans/{keyword_plan}"
   };
 
-  // The resource name of the Keyword Planner plan.
+  // Immutable. The resource name of the Keyword Planner plan.
   // KeywordPlan resource names have the form:
   //
   // `customers/{customer_id}/keywordPlans/{kp_plan_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordPlan"
+    }
+  ];
 
-  // The ID of the keyword plan.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the keyword plan.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the keyword plan.
   //
diff --git a/google/ads/googleads/v3/resources/keyword_plan_ad_group.proto b/google/ads/googleads/v3/resources/keyword_plan_ad_group.proto
index 9db5b425..e0fc2799 100644
--- a/google/ads/googleads/v3/resources/keyword_plan_ad_group.proto
+++ b/google/ads/googleads/v3/resources/keyword_plan_ad_group.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,17 +40,24 @@ message KeywordPlanAdGroup {
     pattern: "customers/{customer}/keywordPlanAdGroups/{keyword_plan_ad_group}"
   };
 
-  // The resource name of the Keyword Planner ad group.
+  // Immutable. The resource name of the Keyword Planner ad group.
   // KeywordPlanAdGroup resource names have the form:
   //
   // `customers/{customer_id}/keywordPlanAdGroups/{kp_ad_group_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordPlanAdGroup"
+    }
+  ];
 
   // The keyword plan campaign to which this ad group belongs.
-  google.protobuf.StringValue keyword_plan_campaign = 2;
+  google.protobuf.StringValue keyword_plan_campaign = 2 [(google.api.resource_reference) = {
+                                                           type: "googleads.googleapis.com/KeywordPlanCampaign"
+                                                         }];
 
-  // The ID of the keyword plan ad group.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the keyword plan ad group.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the keyword plan ad group.
   //
diff --git a/google/ads/googleads/v3/resources/keyword_plan_campaign.proto b/google/ads/googleads/v3/resources/keyword_plan_campaign.proto
index 19ddc15c..b6f93448 100644
--- a/google/ads/googleads/v3/resources/keyword_plan_campaign.proto
+++ b/google/ads/googleads/v3/resources/keyword_plan_campaign.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/keyword_plan_network.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,17 +41,24 @@ message KeywordPlanCampaign {
     pattern: "customers/{customer}/keywordPlanCampaigns/{keyword_plan_campaign}"
   };
 
-  // The resource name of the Keyword Plan campaign.
+  // Immutable. The resource name of the Keyword Plan campaign.
   // KeywordPlanCampaign resource names have the form:
   //
   // `customers/{customer_id}/keywordPlanCampaigns/{kp_campaign_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordPlanCampaign"
+    }
+  ];
 
   // The keyword plan this campaign belongs to.
-  google.protobuf.StringValue keyword_plan = 2;
+  google.protobuf.StringValue keyword_plan = 2 [(google.api.resource_reference) = {
+                                                  type: "googleads.googleapis.com/KeywordPlan"
+                                                }];
 
-  // The ID of the Keyword Plan campaign.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the Keyword Plan campaign.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the Keyword Plan campaign.
   //
@@ -60,7 +68,9 @@ message KeywordPlanCampaign {
 
   // The languages targeted for the Keyword Plan campaign.
   // Max allowed: 1.
-  repeated google.protobuf.StringValue language_constants = 5;
+  repeated google.protobuf.StringValue language_constants = 5 [(google.api.resource_reference) = {
+                                                                 type: "googleads.googleapis.com/LanguageConstant"
+                                                               }];
 
   // Targeting network.
   //
@@ -84,5 +94,7 @@ message KeywordPlanCampaign {
 // Next ID: 3
 message KeywordPlanGeoTarget {
   // Required. The resource name of the geo target.
-  google.protobuf.StringValue geo_target_constant = 1;
+  google.protobuf.StringValue geo_target_constant = 1 [(google.api.resource_reference) = {
+                                                         type: "googleads.googleapis.com/GeoTargetConstant"
+                                                       }];
 }
diff --git a/google/ads/googleads/v3/resources/keyword_plan_keyword.proto b/google/ads/googleads/v3/resources/keyword_plan_keyword.proto
index c3b54e6b..ae4ca903 100644
--- a/google/ads/googleads/v3/resources/keyword_plan_keyword.proto
+++ b/google/ads/googleads/v3/resources/keyword_plan_keyword.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/keyword_match_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,17 +41,24 @@ message KeywordPlanKeyword {
     pattern: "customers/{customer}/keywordPlanKeywords/{keyword_plan_keyword}"
   };
 
-  // The resource name of the Keyword Plan ad group keyword.
+  // Immutable. The resource name of the Keyword Plan ad group keyword.
   // KeywordPlanKeyword resource names have the form:
   //
   // `customers/{customer_id}/keywordPlanKeywords/{kp_ad_group_keyword_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordPlanKeyword"
+    }
+  ];
 
   // The Keyword Plan ad group to which this keyword belongs.
-  google.protobuf.StringValue keyword_plan_ad_group = 2;
+  google.protobuf.StringValue keyword_plan_ad_group = 2 [(google.api.resource_reference) = {
+                                                           type: "googleads.googleapis.com/KeywordPlanAdGroup"
+                                                         }];
 
-  // The ID of the Keyword Plan keyword.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the Keyword Plan keyword.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The keyword text.
   google.protobuf.StringValue text = 4;
diff --git a/google/ads/googleads/v3/resources/keyword_plan_negative_keyword.proto b/google/ads/googleads/v3/resources/keyword_plan_negative_keyword.proto
index 22229f00..8c691bd5 100644
--- a/google/ads/googleads/v3/resources/keyword_plan_negative_keyword.proto
+++ b/google/ads/googleads/v3/resources/keyword_plan_negative_keyword.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/keyword_match_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,17 +41,24 @@ message KeywordPlanNegativeKeyword {
     pattern: "customers/{customer}/keywordPlanNegativeKeywords/{keyword_plan_negative_keyword}"
   };
 
-  // The resource name of the Keyword Plan negative keyword.
+  // Immutable. The resource name of the Keyword Plan negative keyword.
   // KeywordPlanNegativeKeyword resource names have the form:
   //
   // `customers/{customer_id}/keywordPlanNegativeKeywords/{kp_negative_keyword_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordPlanNegativeKeyword"
+    }
+  ];
 
   // The Keyword Plan campaign to which this negative keyword belongs.
-  google.protobuf.StringValue keyword_plan_campaign = 2;
+  google.protobuf.StringValue keyword_plan_campaign = 2 [(google.api.resource_reference) = {
+                                                           type: "googleads.googleapis.com/KeywordPlanCampaign"
+                                                         }];
 
-  // The ID of the Keyword Plan negative keyword.
-  google.protobuf.Int64Value id = 3;
+  // Output only. The ID of the Keyword Plan negative keyword.
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The keyword text.
   google.protobuf.StringValue text = 4;
diff --git a/google/ads/googleads/v3/resources/keyword_view.proto b/google/ads/googleads/v3/resources/keyword_view.proto
index aceb31c4..36701ce0 100644
--- a/google/ads/googleads/v3/resources/keyword_view.proto
+++ b/google/ads/googleads/v3/resources/keyword_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message KeywordView {
     pattern: "customers/{customer}/keywordViews/{keyword_view}"
   };
 
-  // The resource name of the keyword view.
+  // Output only. The resource name of the keyword view.
   // Keyword view resource names have the form:
   //
   // `customers/{customer_id}/keywordViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/KeywordView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/label.proto b/google/ads/googleads/v3/resources/label.proto
index ae7058a5..a75871e9 100644
--- a/google/ads/googleads/v3/resources/label.proto
+++ b/google/ads/googleads/v3/resources/label.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/text_label.proto";
 import "google/ads/googleads/v3/enums/label_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,13 +39,18 @@ message Label {
     pattern: "customers/{customer}/labels/{label}"
   };
 
-  // Name of the resource.
+  // Immutable. Name of the resource.
   // Label resource names have the form:
   // `customers/{customer_id}/labels/{label_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Label"
+    }
+  ];
 
-  // Id of the label. Read only.
-  google.protobuf.Int64Value id = 2;
+  // Output only. Id of the label. Read only.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the label.
   //
@@ -53,8 +59,8 @@ message Label {
   // The length of this string should be between 1 and 80, inclusive.
   google.protobuf.StringValue name = 3;
 
-  // Status of the label. Read only.
-  google.ads.googleads.v3.enums.LabelStatusEnum.LabelStatus status = 4;
+  // Output only. Status of the label. Read only.
+  google.ads.googleads.v3.enums.LabelStatusEnum.LabelStatus status = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // A type of label displaying text on a colored background.
   google.ads.googleads.v3.common.TextLabel text_label = 5;
diff --git a/google/ads/googleads/v3/resources/landing_page_view.proto b/google/ads/googleads/v3/resources/landing_page_view.proto
index c562e160..fda51342 100644
--- a/google/ads/googleads/v3/resources/landing_page_view.proto
+++ b/google/ads/googleads/v3/resources/landing_page_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,12 +40,17 @@ message LandingPageView {
     pattern: "customers/{customer}/landingPageViews/{landing_page_view}"
   };
 
-  // The resource name of the landing page view.
+  // Output only. The resource name of the landing page view.
   // Landing page view resource names have the form:
   //
   // `customers/{customer_id}/landingPageViews/{unexpanded_final_url_fingerprint}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/LandingPageView"
+    }
+  ];
 
-  // The advertiser-specified final URL.
-  google.protobuf.StringValue unexpanded_final_url = 2;
+  // Output only. The advertiser-specified final URL.
+  google.protobuf.StringValue unexpanded_final_url = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/language_constant.proto b/google/ads/googleads/v3/resources/language_constant.proto
index 99700b6d..54eabdbb 100644
--- a/google/ads/googleads/v3/resources/language_constant.proto
+++ b/google/ads/googleads/v3/resources/language_constant.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,22 +39,27 @@ message LanguageConstant {
     pattern: "languageConstants/{language_constant}"
   };
 
-  // The resource name of the language constant.
+  // Output only. The resource name of the language constant.
   // Language constant resource names have the form:
   //
   // `languageConstants/{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/LanguageConstant"
+    }
+  ];
 
-  // The ID of the language constant.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the language constant.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The language code, e.g. "en_US", "en_AU", "es", "fr", etc.
-  google.protobuf.StringValue code = 3;
+  // Output only. The language code, e.g. "en_US", "en_AU", "es", "fr", etc.
+  google.protobuf.StringValue code = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The full name of the language in English, e.g., "English (US)", "Spanish",
+  // Output only. The full name of the language in English, e.g., "English (US)", "Spanish",
   // etc.
-  google.protobuf.StringValue name = 4;
+  google.protobuf.StringValue name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Whether the language is targetable.
-  google.protobuf.BoolValue targetable = 5;
+  // Output only. Whether the language is targetable.
+  google.protobuf.BoolValue targetable = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/location_view.proto b/google/ads/googleads/v3/resources/location_view.proto
index 593c40f4..1405e57c 100644
--- a/google/ads/googleads/v3/resources/location_view.proto
+++ b/google/ads/googleads/v3/resources/location_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -38,9 +39,14 @@ message LocationView {
     pattern: "customers/{customer}/locationViews/{location_view}"
   };
 
-  // The resource name of the location view.
+  // Output only. The resource name of the location view.
   // Location view resource names have the form:
   //
   // `customers/{customer_id}/locationViews/{campaign_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/LocationView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/managed_placement_view.proto b/google/ads/googleads/v3/resources/managed_placement_view.proto
index cda98c6b..2175df46 100644
--- a/google/ads/googleads/v3/resources/managed_placement_view.proto
+++ b/google/ads/googleads/v3/resources/managed_placement_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message ManagedPlacementView {
     pattern: "customers/{customer}/managedPlacementViews/{managed_placement_view}"
   };
 
-  // The resource name of the Managed Placement view.
+  // Output only. The resource name of the Managed Placement view.
   // Managed placement view resource names have the form:
   //
   // `customers/{customer_id}/managedPlacementViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ManagedPlacementView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/media_file.proto b/google/ads/googleads/v3/resources/media_file.proto
index 13628f66..4068912a 100644
--- a/google/ads/googleads/v3/resources/media_file.proto
+++ b/google/ads/googleads/v3/resources/media_file.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/media_type.proto";
 import "google/ads/googleads/v3/enums/mime_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,80 +41,85 @@ message MediaFile {
     pattern: "customers/{customer}/mediaFiles/{media_file}"
   };
 
-  // The resource name of the media file.
+  // Immutable. The resource name of the media file.
   // Media file resource names have the form:
   //
   // `customers/{customer_id}/mediaFiles/{media_file_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/MediaFile"
+    }
+  ];
 
-  // The ID of the media file.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the media file.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Type of the media file.
-  google.ads.googleads.v3.enums.MediaTypeEnum.MediaType type = 5;
+  // Immutable. Type of the media file.
+  google.ads.googleads.v3.enums.MediaTypeEnum.MediaType type = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The mime type of the media file.
-  google.ads.googleads.v3.enums.MimeTypeEnum.MimeType mime_type = 6;
+  // Output only. The mime type of the media file.
+  google.ads.googleads.v3.enums.MimeTypeEnum.MimeType mime_type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The URL of where the original media file was downloaded from (or a file
+  // Immutable. The URL of where the original media file was downloaded from (or a file
   // name). Only used for media of type AUDIO and IMAGE.
-  google.protobuf.StringValue source_url = 7;
+  google.protobuf.StringValue source_url = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The name of the media file. The name can be used by clients to help
+  // Immutable. The name of the media file. The name can be used by clients to help
   // identify previously uploaded media.
-  google.protobuf.StringValue name = 8;
+  google.protobuf.StringValue name = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The size of the media file in bytes.
-  google.protobuf.Int64Value file_size = 9;
+  // Output only. The size of the media file in bytes.
+  google.protobuf.Int64Value file_size = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The specific type of the media file.
   oneof mediatype {
-    // Encapsulates an Image.
-    MediaImage image = 3;
+    // Immutable. Encapsulates an Image.
+    MediaImage image = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-    // A ZIP archive media the content of which contains HTML5 assets.
-    MediaBundle media_bundle = 4;
+    // Immutable. A ZIP archive media the content of which contains HTML5 assets.
+    MediaBundle media_bundle = 4 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Encapsulates an Audio.
-    MediaAudio audio = 10;
+    // Output only. Encapsulates an Audio.
+    MediaAudio audio = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Encapsulates a Video.
-    MediaVideo video = 11;
+    // Immutable. Encapsulates a Video.
+    MediaVideo video = 11 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
 
 // Encapsulates an Image.
 message MediaImage {
-  // Raw image data.
-  google.protobuf.BytesValue data = 1;
+  // Immutable. Raw image data.
+  google.protobuf.BytesValue data = 1 [(google.api.field_behavior) = IMMUTABLE];
 }
 
 // Represents a ZIP archive media the content of which contains HTML5 assets.
 message MediaBundle {
-  // Raw zipped data.
-  google.protobuf.BytesValue data = 1;
+  // Immutable. Raw zipped data.
+  google.protobuf.BytesValue data = 1 [(google.api.field_behavior) = IMMUTABLE];
 }
 
 // Encapsulates an Audio.
 message MediaAudio {
-  // The duration of the Audio in milliseconds.
-  google.protobuf.Int64Value ad_duration_millis = 1;
+  // Output only. The duration of the Audio in milliseconds.
+  google.protobuf.Int64Value ad_duration_millis = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // Encapsulates a Video.
 message MediaVideo {
-  // The duration of the Video in milliseconds.
-  google.protobuf.Int64Value ad_duration_millis = 1;
+  // Output only. The duration of the Video in milliseconds.
+  google.protobuf.Int64Value ad_duration_millis = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The YouTube video ID (as seen in YouTube URLs).
-  google.protobuf.StringValue youtube_video_id = 2;
+  // Immutable. The YouTube video ID (as seen in YouTube URLs).
+  google.protobuf.StringValue youtube_video_id = 2 [(google.api.field_behavior) = IMMUTABLE];
 
-  // The Advertising Digital Identification code for this video, as defined by
+  // Output only. The Advertising Digital Identification code for this video, as defined by
   // the American Association of Advertising Agencies, used mainly for
   // television commercials.
-  google.protobuf.StringValue advertising_id_code = 3;
+  google.protobuf.StringValue advertising_id_code = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The Industry Standard Commercial Identifier code for this video, used
+  // Output only. The Industry Standard Commercial Identifier code for this video, used
   // mainly for television commercials.
-  google.protobuf.StringValue isci_code = 4;
+  google.protobuf.StringValue isci_code = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/merchant_center_link.proto b/google/ads/googleads/v3/resources/merchant_center_link.proto
index 3b5ceaad..a5a8d021 100644
--- a/google/ads/googleads/v3/resources/merchant_center_link.proto
+++ b/google/ads/googleads/v3/resources/merchant_center_link.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/merchant_center_link_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,19 +41,24 @@ message MerchantCenterLink {
     pattern: "customers/{customer}/merchantCenterLinks/{merchant_center_link}"
   };
 
-  // The resource name of the merchant center link.
+  // Immutable. The resource name of the merchant center link.
   // Merchant center link resource names have the form:
   //
   // `customers/{customer_id}/merchantCenterLinks/{merchant_center_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/MerchantCenterLink"
+    }
+  ];
 
-  // The ID of the Merchant Center account.
+  // Output only. The ID of the Merchant Center account.
   // This field is readonly.
-  google.protobuf.Int64Value id = 3;
+  google.protobuf.Int64Value id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name of the Merchant Center account.
+  // Output only. The name of the Merchant Center account.
   // This field is readonly.
-  google.protobuf.StringValue merchant_center_account_name = 4;
+  google.protobuf.StringValue merchant_center_account_name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The status of the link.
   google.ads.googleads.v3.enums.MerchantCenterLinkStatusEnum.MerchantCenterLinkStatus status = 5;
diff --git a/google/ads/googleads/v3/resources/mobile_app_category_constant.proto b/google/ads/googleads/v3/resources/mobile_app_category_constant.proto
index e763be1d..7ae25c91 100644
--- a/google/ads/googleads/v3/resources/mobile_app_category_constant.proto
+++ b/google/ads/googleads/v3/resources/mobile_app_category_constant.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,15 +39,20 @@ message MobileAppCategoryConstant {
     pattern: "mobileAppCategoryConstants/{mobile_app_category_constant}"
   };
 
-  // The resource name of the mobile app category constant.
+  // Output only. The resource name of the mobile app category constant.
   // Mobile app category constant resource names have the form:
   //
   // `mobileAppCategoryConstants/{mobile_app_category_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/MobileAppCategoryConstant"
+    }
+  ];
 
-  // The ID of the mobile app category constant.
-  google.protobuf.Int32Value id = 2;
+  // Output only. The ID of the mobile app category constant.
+  google.protobuf.Int32Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Mobile app category name.
-  google.protobuf.StringValue name = 3;
+  // Output only. Mobile app category name.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/mobile_device_constant.proto b/google/ads/googleads/v3/resources/mobile_device_constant.proto
index 9ece0b3b..71190425 100644
--- a/google/ads/googleads/v3/resources/mobile_device_constant.proto
+++ b/google/ads/googleads/v3/resources/mobile_device_constant.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/mobile_device_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,24 +40,29 @@ message MobileDeviceConstant {
     pattern: "mobileDeviceConstants/{mobile_device_constant}"
   };
 
-  // The resource name of the mobile device constant.
+  // Output only. The resource name of the mobile device constant.
   // Mobile device constant resource names have the form:
   //
   // `mobileDeviceConstants/{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/MobileDeviceConstant"
+    }
+  ];
 
-  // The ID of the mobile device constant.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the mobile device constant.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name of the mobile device.
-  google.protobuf.StringValue name = 3;
+  // Output only. The name of the mobile device.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The manufacturer of the mobile device.
-  google.protobuf.StringValue manufacturer_name = 4;
+  // Output only. The manufacturer of the mobile device.
+  google.protobuf.StringValue manufacturer_name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The operating system of the mobile device.
-  google.protobuf.StringValue operating_system_name = 5;
+  // Output only. The operating system of the mobile device.
+  google.protobuf.StringValue operating_system_name = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of mobile device.
-  google.ads.googleads.v3.enums.MobileDeviceTypeEnum.MobileDeviceType type = 6;
+  // Output only. The type of mobile device.
+  google.ads.googleads.v3.enums.MobileDeviceTypeEnum.MobileDeviceType type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/mutate_job.proto b/google/ads/googleads/v3/resources/mutate_job.proto
index 953eb83b..61a72ca0 100644
--- a/google/ads/googleads/v3/resources/mutate_job.proto
+++ b/google/ads/googleads/v3/resources/mutate_job.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/mutate_job_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -44,46 +45,51 @@ message MutateJob {
   // Additional information about the mutate job. This message is also used as
   // metadata returned in mutate job Long Running Operations.
   message MutateJobMetadata {
-    // The time when this mutate job was created.
+    // Output only. The time when this mutate job was created.
     // Formatted as yyyy-mm-dd hh:mm:ss. Example: "2018-03-05 09:15:00"
-    google.protobuf.StringValue creation_date_time = 1;
+    google.protobuf.StringValue creation_date_time = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The time when this mutate job was completed.
+    // Output only. The time when this mutate job was completed.
     // Formatted as yyyy-MM-dd HH:mm:ss. Example: "2018-03-05 09:16:00"
-    google.protobuf.StringValue completion_date_time = 2;
+    google.protobuf.StringValue completion_date_time = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The fraction (between 0.0 and 1.0) of mutates that have been processed.
+    // Output only. The fraction (between 0.0 and 1.0) of mutates that have been processed.
     // This is empty if the job hasn't started running yet.
-    google.protobuf.DoubleValue estimated_completion_ratio = 3;
+    google.protobuf.DoubleValue estimated_completion_ratio = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The number of mutate operations in the mutate job.
-    google.protobuf.Int64Value operation_count = 4;
+    // Output only. The number of mutate operations in the mutate job.
+    google.protobuf.Int64Value operation_count = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The number of mutate operations executed by the mutate job.
+    // Output only. The number of mutate operations executed by the mutate job.
     // Present only if the job has started running.
-    google.protobuf.Int64Value executed_operation_count = 5;
+    google.protobuf.Int64Value executed_operation_count = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The resource name of the mutate job.
+  // Immutable. The resource name of the mutate job.
   // Mutate job resource names have the form:
   //
   // `customers/{customer_id}/mutateJobs/{mutate_job_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/MutateJob"
+    }
+  ];
 
-  // ID of this mutate job.
-  google.protobuf.Int64Value id = 2;
+  // Output only. ID of this mutate job.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The next sequence token to use when adding operations. Only set when the
+  // Output only. The next sequence token to use when adding operations. Only set when the
   // mutate job status is PENDING.
-  google.protobuf.StringValue next_add_sequence_token = 3;
+  google.protobuf.StringValue next_add_sequence_token = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Contains additional information about this mutate job.
-  MutateJobMetadata metadata = 4;
+  // Output only. Contains additional information about this mutate job.
+  MutateJobMetadata metadata = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Status of this mutate job.
-  google.ads.googleads.v3.enums.MutateJobStatusEnum.MutateJobStatus status = 5;
+  // Output only. Status of this mutate job.
+  google.ads.googleads.v3.enums.MutateJobStatusEnum.MutateJobStatus status = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The resource name of the long-running operation that can be used to poll
+  // Output only. The resource name of the long-running operation that can be used to poll
   // for completion. Only set when the mutate job status is RUNNING or DONE.
-  google.protobuf.StringValue long_running_operation = 6;
+  google.protobuf.StringValue long_running_operation = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/operating_system_version_constant.proto b/google/ads/googleads/v3/resources/operating_system_version_constant.proto
index e863b46f..cb9ed40b 100644
--- a/google/ads/googleads/v3/resources/operating_system_version_constant.proto
+++ b/google/ads/googleads/v3/resources/operating_system_version_constant.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/operating_system_version_operator_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,25 +42,30 @@ message OperatingSystemVersionConstant {
     pattern: "operatingSystemVersionConstants/{operating_system_version_constant}"
   };
 
-  // The resource name of the operating system version constant.
+  // Output only. The resource name of the operating system version constant.
   // Operating system version constant resource names have the form:
   //
   // `operatingSystemVersionConstants/{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/OperatingSystemVersionConstant"
+    }
+  ];
 
-  // The ID of the operating system version.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the operating system version.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Name of the operating system.
-  google.protobuf.StringValue name = 3;
+  // Output only. Name of the operating system.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The OS Major Version number.
-  google.protobuf.Int32Value os_major_version = 4;
+  // Output only. The OS Major Version number.
+  google.protobuf.Int32Value os_major_version = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The OS Minor Version number.
-  google.protobuf.Int32Value os_minor_version = 5;
+  // Output only. The OS Minor Version number.
+  google.protobuf.Int32Value os_minor_version = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Determines whether this constant represents a single version or a range of
+  // Output only. Determines whether this constant represents a single version or a range of
   // versions.
-  google.ads.googleads.v3.enums.OperatingSystemVersionOperatorTypeEnum.OperatingSystemVersionOperatorType operator_type = 6;
+  google.ads.googleads.v3.enums.OperatingSystemVersionOperatorTypeEnum.OperatingSystemVersionOperatorType operator_type = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/paid_organic_search_term_view.proto b/google/ads/googleads/v3/resources/paid_organic_search_term_view.proto
index fa5e0d1b..0bb04738 100644
--- a/google/ads/googleads/v3/resources/paid_organic_search_term_view.proto
+++ b/google/ads/googleads/v3/resources/paid_organic_search_term_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -39,13 +40,18 @@ message PaidOrganicSearchTermView {
     pattern: "customers/{customer}/paidOrganicSearchTermViews/{paid_organic_search_term_view}"
   };
 
-  // The resource name of the search term view.
+  // Output only. The resource name of the search term view.
   // Search term view resource names have the form:
   //
   // `customers/{customer_id}/paidOrganicSearchTermViews/{campaign_id}~
   // {ad_group_id}~{URL-base64 search term}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/PaidOrganicSearchTermView"
+    }
+  ];
 
-  // The search term.
-  google.protobuf.StringValue search_term = 2;
+  // Output only. The search term.
+  google.protobuf.StringValue search_term = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/parental_status_view.proto b/google/ads/googleads/v3/resources/parental_status_view.proto
index c3b58860..8aae34db 100644
--- a/google/ads/googleads/v3/resources/parental_status_view.proto
+++ b/google/ads/googleads/v3/resources/parental_status_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message ParentalStatusView {
     pattern: "customers/{customer}/parentalStatusViews/{parental_status_view}"
   };
 
-  // The resource name of the parental status view.
+  // Output only. The resource name of the parental status view.
   // Parental Status view resource names have the form:
   //
   // `customers/{customer_id}/parentalStatusViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ParentalStatusView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/payments_account.proto b/google/ads/googleads/v3/resources/payments_account.proto
index 18b8550a..6cbf58ae 100644
--- a/google/ads/googleads/v3/resources/payments_account.proto
+++ b/google/ads/googleads/v3/resources/payments_account.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,28 +39,33 @@ message PaymentsAccount {
     pattern: "customers/{customer}/paymentsAccounts/{payments_account}"
   };
 
-  // The resource name of the payments account.
+  // Output only. The resource name of the payments account.
   // PaymentsAccount resource names have the form:
   //
   // `customers/{customer_id}/paymentsAccounts/{payments_account_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/PaymentsAccount"
+    }
+  ];
 
-  // A 16 digit ID used to identify a payments account.
-  google.protobuf.StringValue payments_account_id = 2;
+  // Output only. A 16 digit ID used to identify a payments account.
+  google.protobuf.StringValue payments_account_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name of the payments account.
-  google.protobuf.StringValue name = 3;
+  // Output only. The name of the payments account.
+  google.protobuf.StringValue name = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The currency code of the payments account.
+  // Output only. The currency code of the payments account.
   // A subset of the currency codes derived from the ISO 4217 standard is
   // supported.
-  google.protobuf.StringValue currency_code = 4;
+  google.protobuf.StringValue currency_code = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A 12 digit ID used to identify the payments profile associated with the
+  // Output only. A 12 digit ID used to identify the payments profile associated with the
   // payments account.
-  google.protobuf.StringValue payments_profile_id = 5;
+  google.protobuf.StringValue payments_profile_id = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A secondary payments profile ID present in uncommon situations, e.g.
+  // Output only. A secondary payments profile ID present in uncommon situations, e.g.
   // when a sequential liability agreement has been arranged.
-  google.protobuf.StringValue secondary_payments_profile_id = 6;
+  google.protobuf.StringValue secondary_payments_profile_id = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/product_bidding_category_constant.proto b/google/ads/googleads/v3/resources/product_bidding_category_constant.proto
index 7bc3e8b4..149fb016 100644
--- a/google/ads/googleads/v3/resources/product_bidding_category_constant.proto
+++ b/google/ads/googleads/v3/resources/product_bidding_category_constant.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/product_bidding_category_level.proto";
 import "google/ads/googleads/v3/enums/product_bidding_category_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,34 +41,44 @@ message ProductBiddingCategoryConstant {
     pattern: "productBiddingCategoryConstants/{product_bidding_category_constant}"
   };
 
-  // The resource name of the product bidding category.
+  // Output only. The resource name of the product bidding category.
   // Product bidding category resource names have the form:
   //
   // `productBiddingCategoryConstants/{country_code}~{level}~{id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ProductBiddingCategoryConstant"
+    }
+  ];
 
-  // ID of the product bidding category.
+  // Output only. ID of the product bidding category.
   //
   // This ID is equivalent to the google_product_category ID as described in
   // this article: https://support.google.com/merchants/answer/6324436.
-  google.protobuf.Int64Value id = 2;
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Two-letter upper-case country code of the product bidding category.
-  google.protobuf.StringValue country_code = 3;
+  // Output only. Two-letter upper-case country code of the product bidding category.
+  google.protobuf.StringValue country_code = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Resource name of the parent product bidding category.
-  google.protobuf.StringValue product_bidding_category_constant_parent = 4;
+  // Output only. Resource name of the parent product bidding category.
+  google.protobuf.StringValue product_bidding_category_constant_parent = 4 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ProductBiddingCategoryConstant"
+    }
+  ];
 
-  // Level of the product bidding category.
-  google.ads.googleads.v3.enums.ProductBiddingCategoryLevelEnum.ProductBiddingCategoryLevel level = 5;
+  // Output only. Level of the product bidding category.
+  google.ads.googleads.v3.enums.ProductBiddingCategoryLevelEnum.ProductBiddingCategoryLevel level = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Status of the product bidding category.
-  google.ads.googleads.v3.enums.ProductBiddingCategoryStatusEnum.ProductBiddingCategoryStatus status = 6;
+  // Output only. Status of the product bidding category.
+  google.ads.googleads.v3.enums.ProductBiddingCategoryStatusEnum.ProductBiddingCategoryStatus status = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Language code of the product bidding category.
-  google.protobuf.StringValue language_code = 7;
+  // Output only. Language code of the product bidding category.
+  google.protobuf.StringValue language_code = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Display value of the product bidding category localized according to
+  // Output only. Display value of the product bidding category localized according to
   // language_code.
-  google.protobuf.StringValue localized_name = 8;
+  google.protobuf.StringValue localized_name = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/product_group_view.proto b/google/ads/googleads/v3/resources/product_group_view.proto
index c5afc82e..2572a3fb 100644
--- a/google/ads/googleads/v3/resources/product_group_view.proto
+++ b/google/ads/googleads/v3/resources/product_group_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message ProductGroupView {
     pattern: "customers/{customer}/productGroupViews/{product_group_view}"
   };
 
-  // The resource name of the product group view.
+  // Output only. The resource name of the product group view.
   // Product group view resource names have the form:
   //
   // `customers/{customer_id}/productGroupViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ProductGroupView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/recommendation.proto b/google/ads/googleads/v3/resources/recommendation.proto
index fa6fb560..13cfb04e 100644
--- a/google/ads/googleads/v3/resources/recommendation.proto
+++ b/google/ads/googleads/v3/resources/recommendation.proto
@@ -22,6 +22,7 @@ import "google/ads/googleads/v3/enums/keyword_match_type.proto";
 import "google/ads/googleads/v3/enums/recommendation_type.proto";
 import "google/ads/googleads/v3/enums/target_cpa_opt_in_recommendation_goal.proto";
 import "google/ads/googleads/v3/resources/ad.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -47,133 +48,114 @@ message Recommendation {
   // The impact of making the change as described in the recommendation.
   // Some types of recommendations may not have impact information.
   message RecommendationImpact {
-    // Base metrics at the time the recommendation was generated.
-    RecommendationMetrics base_metrics = 1;
+    // Output only. Base metrics at the time the recommendation was generated.
+    RecommendationMetrics base_metrics = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Estimated metrics if the recommendation is applied.
-    RecommendationMetrics potential_metrics = 2;
+    // Output only. Estimated metrics if the recommendation is applied.
+    RecommendationMetrics potential_metrics = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // Weekly account performance metrics. For some recommendation types, these
   // are averaged over the past 90-day period and hence can be fractional.
   message RecommendationMetrics {
-    // Number of ad impressions.
-    google.protobuf.DoubleValue impressions = 1;
+    // Output only. Number of ad impressions.
+    google.protobuf.DoubleValue impressions = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Number of ad clicks.
-    google.protobuf.DoubleValue clicks = 2;
+    // Output only. Number of ad clicks.
+    google.protobuf.DoubleValue clicks = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Cost (in micros) for advertising, in the local currency for the account.
-    google.protobuf.Int64Value cost_micros = 3;
+    // Output only. Cost (in micros) for advertising, in the local currency for the account.
+    google.protobuf.Int64Value cost_micros = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Number of conversions.
-    google.protobuf.DoubleValue conversions = 4;
+    // Output only. Number of conversions.
+    google.protobuf.DoubleValue conversions = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Number of video views for a video ad campaign.
-    google.protobuf.DoubleValue video_views = 5;
+    // Output only. Number of video views for a video ad campaign.
+    google.protobuf.DoubleValue video_views = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The budget recommendation for budget constrained campaigns.
   message CampaignBudgetRecommendation {
     // The impact estimates for a given budget amount.
     message CampaignBudgetRecommendationOption {
-      // The budget amount for this option.
-      google.protobuf.Int64Value budget_amount_micros = 1;
+      // Output only. The budget amount for this option.
+      google.protobuf.Int64Value budget_amount_micros = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // The impact estimate if budget is changed to amount specified in this
+      // Output only. The impact estimate if budget is changed to amount specified in this
       // option.
-      RecommendationImpact impact = 2;
+      RecommendationImpact impact = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
     }
 
-    // The current budget amount in micros.
-    google.protobuf.Int64Value current_budget_amount_micros = 1;
+    // Output only. The current budget amount in micros.
+    google.protobuf.Int64Value current_budget_amount_micros = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The recommended budget amount in micros.
-    google.protobuf.Int64Value recommended_budget_amount_micros = 2;
+    // Output only. The recommended budget amount in micros.
+    google.protobuf.Int64Value recommended_budget_amount_micros = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The budget amounts and associated impact estimates for some values of
+    // Output only. The budget amounts and associated impact estimates for some values of
     // possible budget amounts.
-    repeated CampaignBudgetRecommendationOption budget_options = 3;
+    repeated CampaignBudgetRecommendationOption budget_options = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The keyword recommendation.
   message KeywordRecommendation {
-    // The recommended keyword.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 1;
+    // Output only. The recommended keyword.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The recommended CPC (cost-per-click) bid.
-    google.protobuf.Int64Value recommended_cpc_bid_micros = 2;
+    // Output only. The recommended CPC (cost-per-click) bid.
+    google.protobuf.Int64Value recommended_cpc_bid_micros = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The Maximize Clicks opt-in recommendation.
-  message MaximizeClicksOptInRecommendation {
-    // The recommended new budget amount.
-    // Only set if the current budget is too high.
-    google.protobuf.Int64Value recommended_budget_amount_micros = 1;
+  // The keyword match type recommendation.
+  message KeywordMatchTypeRecommendation {
+    // Output only. The existing keyword where the match type should be more broad.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
+
+    // Output only. The recommended new match type.
+    google.ads.googleads.v3.enums.KeywordMatchTypeEnum.KeywordMatchType recommended_match_type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The text ad recommendation.
   message TextAdRecommendation {
-    // Recommended ad.
-    Ad ad = 1;
+    // Output only. Recommended ad.
+    Ad ad = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Creation date of the recommended ad.
+    // Output only. Creation date of the recommended ad.
     // YYYY-MM-DD format, e.g., 2018-04-17.
-    google.protobuf.StringValue creation_date = 2;
+    google.protobuf.StringValue creation_date = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Date, if present, is the earliest when the recommendation will be auto
+    // Output only. Date, if present, is the earliest when the recommendation will be auto
     // applied.
     // YYYY-MM-DD format, e.g., 2018-04-17.
-    google.protobuf.StringValue auto_apply_date = 3;
-  }
-
-  // The move unused budget recommendation.
-  message MoveUnusedBudgetRecommendation {
-    // The excess budget's resource_name.
-    google.protobuf.StringValue excess_campaign_budget = 1;
-
-    // The recommendation for the constrained budget to increase.
-    CampaignBudgetRecommendation budget_recommendation = 2;
+    google.protobuf.StringValue auto_apply_date = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The Target CPA opt-in recommendation.
   message TargetCpaOptInRecommendation {
     // The Target CPA opt-in option with impact estimate.
     message TargetCpaOptInRecommendationOption {
-      // The goal achieved by this option.
-      google.ads.googleads.v3.enums.TargetCpaOptInRecommendationGoalEnum.TargetCpaOptInRecommendationGoal goal = 1;
+      // Output only. The goal achieved by this option.
+      google.ads.googleads.v3.enums.TargetCpaOptInRecommendationGoalEnum.TargetCpaOptInRecommendationGoal goal = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // Average CPA target.
-      google.protobuf.Int64Value target_cpa_micros = 2;
+      // Output only. Average CPA target.
+      google.protobuf.Int64Value target_cpa_micros = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // The minimum campaign budget, in local currency for the account,
+      // Output only. The minimum campaign budget, in local currency for the account,
       // required to achieve the target CPA.
       // Amount is specified in micros, where one million is equivalent to one
       // currency unit.
-      google.protobuf.Int64Value required_campaign_budget_amount_micros = 3;
+      google.protobuf.Int64Value required_campaign_budget_amount_micros = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-      // The impact estimate if this option is selected.
-      RecommendationImpact impact = 4;
+      // Output only. The impact estimate if this option is selected.
+      RecommendationImpact impact = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
     }
 
-    // The available goals and corresponding options for Target CPA strategy.
-    repeated TargetCpaOptInRecommendationOption options = 1;
+    // Output only. The available goals and corresponding options for Target CPA strategy.
+    repeated TargetCpaOptInRecommendationOption options = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The recommended average CPA target. See required budget amount and impact
+    // Output only. The recommended average CPA target. See required budget amount and impact
     // of using this recommendation in options list.
-    google.protobuf.Int64Value recommended_target_cpa_micros = 2;
-  }
-
-  // The Callout extension recommendation.
-  message CalloutExtensionRecommendation {
-    // Callout extensions recommended to be added.
-    repeated google.ads.googleads.v3.common.CalloutFeedItem recommended_extensions = 1;
-  }
-
-  // The Maximize Conversions Opt-In recommendation.
-  message MaximizeConversionsOptInRecommendation {
-    // The recommended new budget amount.
-    google.protobuf.Int64Value recommended_budget_amount_micros = 1;
+    google.protobuf.Int64Value recommended_target_cpa_micros = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The Enhanced Cost-Per-Click Opt-In recommendation.
@@ -181,18 +163,19 @@ message Recommendation {
 
   }
 
-  // The keyword match type recommendation.
-  message KeywordMatchTypeRecommendation {
-    // The existing keyword where the match type should be more broad.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 1;
-
-    // The recommended new match type.
-    google.ads.googleads.v3.enums.KeywordMatchTypeEnum.KeywordMatchType recommended_match_type = 2;
+  // The Maximize Conversions Opt-In recommendation.
+  message MaximizeConversionsOptInRecommendation {
+    // Output only. The recommended new budget amount.
+    google.protobuf.Int64Value recommended_budget_amount_micros = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The Search Partners Opt-In recommendation.
-  message SearchPartnersOptInRecommendation {
+  // The move unused budget recommendation.
+  message MoveUnusedBudgetRecommendation {
+    // Output only. The excess budget's resource_name.
+    google.protobuf.StringValue excess_campaign_budget = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
 
+    // Output only. The recommendation for the constrained budget to increase.
+    CampaignBudgetRecommendation budget_recommendation = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The Optimize Ad Rotation recommendation.
@@ -200,38 +183,66 @@ message Recommendation {
 
   }
 
+  // The Search Partners Opt-In recommendation.
+  message SearchPartnersOptInRecommendation {
+
+  }
+
+  // The Maximize Clicks opt-in recommendation.
+  message MaximizeClicksOptInRecommendation {
+    // Output only. The recommended new budget amount.
+    // Only set if the current budget is too high.
+    google.protobuf.Int64Value recommended_budget_amount_micros = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
+  }
+
+  // The Callout extension recommendation.
+  message CalloutExtensionRecommendation {
+    // Output only. Callout extensions recommended to be added.
+    repeated google.ads.googleads.v3.common.CalloutFeedItem recommended_extensions = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
+  }
+
   // The Sitelink extension recommendation.
   message SitelinkExtensionRecommendation {
-    // Sitelink extensions recommended to be added.
-    repeated google.ads.googleads.v3.common.SitelinkFeedItem recommended_extensions = 1;
+    // Output only. Sitelink extensions recommended to be added.
+    repeated google.ads.googleads.v3.common.SitelinkFeedItem recommended_extensions = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
   // The Call extension recommendation.
   message CallExtensionRecommendation {
-    // Call extensions recommended to be added.
-    repeated google.ads.googleads.v3.common.CallFeedItem recommended_extensions = 1;
+    // Output only. Call extensions recommended to be added.
+    repeated google.ads.googleads.v3.common.CallFeedItem recommended_extensions = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 
-  // The resource name of the recommendation.
+  // Immutable. The resource name of the recommendation.
   //
   // `customers/{customer_id}/recommendations/{recommendation_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Recommendation"
+    }
+  ];
 
-  // The type of recommendation.
-  google.ads.googleads.v3.enums.RecommendationTypeEnum.RecommendationType type = 2;
+  // Output only. The type of recommendation.
+  google.ads.googleads.v3.enums.RecommendationTypeEnum.RecommendationType type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The impact on account performance as a result of applying the
+  // Output only. The impact on account performance as a result of applying the
   // recommendation.
-  RecommendationImpact impact = 3;
+  RecommendationImpact impact = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The budget targeted by this recommendation. This will be set only when
+  // Output only. The budget targeted by this recommendation. This will be set only when
   // the recommendation affects a single campaign budget.
   //
   // This field will be set for the following recommendation types:
   // CAMPAIGN_BUDGET, MOVE_UNUSED_BUDGET
-  google.protobuf.StringValue campaign_budget = 5;
+  google.protobuf.StringValue campaign_budget = 5 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/CampaignBudget"
+    }
+  ];
 
-  // The campaign targeted by this recommendation. This will be set only when
+  // Output only. The campaign targeted by this recommendation. This will be set only when
   // the recommendation affects a single campaign.
   //
   // This field will be set for the following recommendation types:
@@ -239,60 +250,70 @@ message Recommendation {
   // KEYWORD_MATCH_TYPE, MAXIMIZE_CLICKS_OPT_IN, MAXIMIZE_CONVERSIONS_OPT_IN,
   // OPTIMIZE_AD_ROTATION, SEARCH_PARTNERS_OPT_IN, SITELINK_EXTENSION,
   // TARGET_CPA_OPT_IN, TEXT_AD
-  google.protobuf.StringValue campaign = 6;
+  google.protobuf.StringValue campaign = 6 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Campaign"
+    }
+  ];
 
-  // The ad group targeted by this recommendation. This will be set only when
+  // Output only. The ad group targeted by this recommendation. This will be set only when
   // the recommendation affects a single ad group.
   //
   // This field will be set for the following recommendation types:
   // KEYWORD, OPTIMIZE_AD_ROTATION, TEXT_AD
-  google.protobuf.StringValue ad_group = 7;
+  google.protobuf.StringValue ad_group = 7 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // Whether the recommendation is dismissed or not.
-  google.protobuf.BoolValue dismissed = 13;
+  // Output only. Whether the recommendation is dismissed or not.
+  google.protobuf.BoolValue dismissed = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The details of recommendation.
   oneof recommendation {
-    // The campaign budget recommendation.
-    CampaignBudgetRecommendation campaign_budget_recommendation = 4;
+    // Output only. The campaign budget recommendation.
+    CampaignBudgetRecommendation campaign_budget_recommendation = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The keyword recommendation.
-    KeywordRecommendation keyword_recommendation = 8;
+    // Output only. The keyword recommendation.
+    KeywordRecommendation keyword_recommendation = 8 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // Add expanded text ad recommendation.
-    TextAdRecommendation text_ad_recommendation = 9;
+    // Output only. Add expanded text ad recommendation.
+    TextAdRecommendation text_ad_recommendation = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The TargetCPA opt-in recommendation.
-    TargetCpaOptInRecommendation target_cpa_opt_in_recommendation = 10;
+    // Output only. The TargetCPA opt-in recommendation.
+    TargetCpaOptInRecommendation target_cpa_opt_in_recommendation = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The MaximizeConversions Opt-In recommendation.
-    MaximizeConversionsOptInRecommendation maximize_conversions_opt_in_recommendation = 11;
+    // Output only. The MaximizeConversions Opt-In recommendation.
+    MaximizeConversionsOptInRecommendation maximize_conversions_opt_in_recommendation = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Enhanced Cost-Per-Click Opt-In recommendation.
-    EnhancedCpcOptInRecommendation enhanced_cpc_opt_in_recommendation = 12;
+    // Output only. The Enhanced Cost-Per-Click Opt-In recommendation.
+    EnhancedCpcOptInRecommendation enhanced_cpc_opt_in_recommendation = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Search Partners Opt-In recommendation.
-    SearchPartnersOptInRecommendation search_partners_opt_in_recommendation = 14;
+    // Output only. The Search Partners Opt-In recommendation.
+    SearchPartnersOptInRecommendation search_partners_opt_in_recommendation = 14 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The MaximizeClicks Opt-In recommendation.
-    MaximizeClicksOptInRecommendation maximize_clicks_opt_in_recommendation = 15;
+    // Output only. The MaximizeClicks Opt-In recommendation.
+    MaximizeClicksOptInRecommendation maximize_clicks_opt_in_recommendation = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Optimize Ad Rotation recommendation.
-    OptimizeAdRotationRecommendation optimize_ad_rotation_recommendation = 16;
+    // Output only. The Optimize Ad Rotation recommendation.
+    OptimizeAdRotationRecommendation optimize_ad_rotation_recommendation = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Callout extension recommendation.
-    CalloutExtensionRecommendation callout_extension_recommendation = 17;
+    // Output only. The Callout extension recommendation.
+    CalloutExtensionRecommendation callout_extension_recommendation = 17 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Sitelink extension recommendation.
-    SitelinkExtensionRecommendation sitelink_extension_recommendation = 18;
+    // Output only. The Sitelink extension recommendation.
+    SitelinkExtensionRecommendation sitelink_extension_recommendation = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The Call extension recommendation.
-    CallExtensionRecommendation call_extension_recommendation = 19;
+    // Output only. The Call extension recommendation.
+    CallExtensionRecommendation call_extension_recommendation = 19 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The keyword match type recommendation.
-    KeywordMatchTypeRecommendation keyword_match_type_recommendation = 20;
+    // Output only. The keyword match type recommendation.
+    KeywordMatchTypeRecommendation keyword_match_type_recommendation = 20 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-    // The move unused budget recommendation.
-    MoveUnusedBudgetRecommendation move_unused_budget_recommendation = 21;
+    // Output only. The move unused budget recommendation.
+    MoveUnusedBudgetRecommendation move_unused_budget_recommendation = 21 [(google.api.field_behavior) = OUTPUT_ONLY];
   }
 }
diff --git a/google/ads/googleads/v3/resources/remarketing_action.proto b/google/ads/googleads/v3/resources/remarketing_action.proto
index 7981e2ce..e1aff0a8 100644
--- a/google/ads/googleads/v3/resources/remarketing_action.proto
+++ b/google/ads/googleads/v3/resources/remarketing_action.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/tag_snippet.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,14 +42,19 @@ message RemarketingAction {
     pattern: "customers/{customer}/remarketingActions/{remarketing_action}"
   };
 
-  // The resource name of the remarketing action.
+  // Immutable. The resource name of the remarketing action.
   // Remarketing action resource names have the form:
   //
   // `customers/{customer_id}/remarketingActions/{remarketing_action_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/RemarketingAction"
+    }
+  ];
 
-  // Id of the remarketing action.
-  google.protobuf.Int64Value id = 2;
+  // Output only. Id of the remarketing action.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The name of the remarketing action.
   //
@@ -56,6 +62,6 @@ message RemarketingAction {
   // remarketing actions.
   google.protobuf.StringValue name = 3;
 
-  // The snippets used for tracking remarketing actions.
-  repeated google.ads.googleads.v3.common.TagSnippet tag_snippets = 4;
+  // Output only. The snippets used for tracking remarketing actions.
+  repeated google.ads.googleads.v3.common.TagSnippet tag_snippets = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/search_term_view.proto b/google/ads/googleads/v3/resources/search_term_view.proto
index 02668a9f..11125bc9 100644
--- a/google/ads/googleads/v3/resources/search_term_view.proto
+++ b/google/ads/googleads/v3/resources/search_term_view.proto
@@ -17,6 +17,7 @@ syntax = "proto3";
 package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/search_term_targeting_status.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,19 +41,29 @@ message SearchTermView {
     pattern: "customers/{customer}/searchTermViews/{search_term_view}"
   };
 
-  // The resource name of the search term view.
+  // Output only. The resource name of the search term view.
   // Search term view resource names have the form:
   //
   // `customers/{customer_id}/searchTermViews/{campaign_id}~{ad_group_id}~{URL-base64_search_term}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/SearchTermView"
+    }
+  ];
 
-  // The search term.
-  google.protobuf.StringValue search_term = 2;
+  // Output only. The search term.
+  google.protobuf.StringValue search_term = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ad group the search term served in.
-  google.protobuf.StringValue ad_group = 3;
+  // Output only. The ad group the search term served in.
+  google.protobuf.StringValue ad_group = 3 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/AdGroup"
+    }
+  ];
 
-  // Indicates whether the search term is currently one of your
+  // Output only. Indicates whether the search term is currently one of your
   // targeted or excluded keywords.
-  google.ads.googleads.v3.enums.SearchTermTargetingStatusEnum.SearchTermTargetingStatus status = 4;
+  google.ads.googleads.v3.enums.SearchTermTargetingStatusEnum.SearchTermTargetingStatus status = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/shared_criterion.proto b/google/ads/googleads/v3/resources/shared_criterion.proto
index 5d0474db..25baf4a4 100644
--- a/google/ads/googleads/v3/resources/shared_criterion.proto
+++ b/google/ads/googleads/v3/resources/shared_criterion.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/criteria.proto";
 import "google/ads/googleads/v3/enums/criterion_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,43 +41,53 @@ message SharedCriterion {
     pattern: "customers/{customer}/sharedCriteria/{shared_criterion}"
   };
 
-  // The resource name of the shared criterion.
+  // Immutable. The resource name of the shared criterion.
   // Shared set resource names have the form:
   //
   // `customers/{customer_id}/sharedCriteria/{shared_set_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/SharedCriterion"
+    }
+  ];
 
-  // The shared set to which the shared criterion belongs.
-  google.protobuf.StringValue shared_set = 2;
+  // Immutable. The shared set to which the shared criterion belongs.
+  google.protobuf.StringValue shared_set = 2 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/SharedSet"
+    }
+  ];
 
-  // The ID of the criterion.
+  // Output only. The ID of the criterion.
   //
   // This field is ignored for mutates.
-  google.protobuf.Int64Value criterion_id = 26;
+  google.protobuf.Int64Value criterion_id = 26 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of the criterion.
-  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 4;
+  // Output only. The type of the criterion.
+  google.ads.googleads.v3.enums.CriterionTypeEnum.CriterionType type = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The criterion.
   //
   // Exactly one must be set.
   oneof criterion {
-    // Keyword.
-    google.ads.googleads.v3.common.KeywordInfo keyword = 3;
+    // Immutable. Keyword.
+    google.ads.googleads.v3.common.KeywordInfo keyword = 3 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Video.
-    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 5;
+    // Immutable. YouTube Video.
+    google.ads.googleads.v3.common.YouTubeVideoInfo youtube_video = 5 [(google.api.field_behavior) = IMMUTABLE];
 
-    // YouTube Channel.
-    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 6;
+    // Immutable. YouTube Channel.
+    google.ads.googleads.v3.common.YouTubeChannelInfo youtube_channel = 6 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Placement.
-    google.ads.googleads.v3.common.PlacementInfo placement = 7;
+    // Immutable. Placement.
+    google.ads.googleads.v3.common.PlacementInfo placement = 7 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile App Category.
-    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 8;
+    // Immutable. Mobile App Category.
+    google.ads.googleads.v3.common.MobileAppCategoryInfo mobile_app_category = 8 [(google.api.field_behavior) = IMMUTABLE];
 
-    // Mobile application.
-    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 9;
+    // Immutable. Mobile application.
+    google.ads.googleads.v3.common.MobileApplicationInfo mobile_application = 9 [(google.api.field_behavior) = IMMUTABLE];
   }
 }
diff --git a/google/ads/googleads/v3/resources/shared_set.proto b/google/ads/googleads/v3/resources/shared_set.proto
index f1a8bfc3..0ec8bc63 100644
--- a/google/ads/googleads/v3/resources/shared_set.proto
+++ b/google/ads/googleads/v3/resources/shared_set.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/enums/shared_set_status.proto";
 import "google/ads/googleads/v3/enums/shared_set_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -41,18 +42,23 @@ message SharedSet {
     pattern: "customers/{customer}/sharedSets/{shared_set}"
   };
 
-  // The resource name of the shared set.
+  // Immutable. The resource name of the shared set.
   // Shared set resource names have the form:
   //
   // `customers/{customer_id}/sharedSets/{shared_set_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/SharedSet"
+    }
+  ];
 
-  // The ID of this shared set. Read only.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of this shared set. Read only.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The type of this shared set: each shared set holds only a single kind
+  // Immutable. The type of this shared set: each shared set holds only a single kind
   // of resource. Required. Immutable.
-  google.ads.googleads.v3.enums.SharedSetTypeEnum.SharedSetType type = 3;
+  google.ads.googleads.v3.enums.SharedSetTypeEnum.SharedSetType type = 3 [(google.api.field_behavior) = IMMUTABLE];
 
   // The name of this shared set. Required.
   // Shared Sets must have names that are unique among active shared sets of
@@ -61,12 +67,12 @@ message SharedSet {
   // inclusive.
   google.protobuf.StringValue name = 4;
 
-  // The status of this shared set. Read only.
-  google.ads.googleads.v3.enums.SharedSetStatusEnum.SharedSetStatus status = 5;
+  // Output only. The status of this shared set. Read only.
+  google.ads.googleads.v3.enums.SharedSetStatusEnum.SharedSetStatus status = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The number of shared criteria within this shared set. Read only.
-  google.protobuf.Int64Value member_count = 6;
+  // Output only. The number of shared criteria within this shared set. Read only.
+  google.protobuf.Int64Value member_count = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The number of campaigns associated with this shared set. Read only.
-  google.protobuf.Int64Value reference_count = 7;
+  // Output only. The number of campaigns associated with this shared set. Read only.
+  google.protobuf.Int64Value reference_count = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/shopping_performance_view.proto b/google/ads/googleads/v3/resources/shopping_performance_view.proto
index 6926548d..e794512d 100644
--- a/google/ads/googleads/v3/resources/shopping_performance_view.proto
+++ b/google/ads/googleads/v3/resources/shopping_performance_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -42,8 +43,13 @@ message ShoppingPerformanceView {
     pattern: "customers/{customer}/shoppingPerformanceView"
   };
 
-  // The resource name of the Shopping performance view.
+  // Output only. The resource name of the Shopping performance view.
   // Shopping performance view resource names have the form:
   // `customers/{customer_id}/shoppingPerformanceView`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/ShoppingPerformanceView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/topic_constant.proto b/google/ads/googleads/v3/resources/topic_constant.proto
index 1d805756..a20f7706 100644
--- a/google/ads/googleads/v3/resources/topic_constant.proto
+++ b/google/ads/googleads/v3/resources/topic_constant.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,22 +41,32 @@ message TopicConstant {
     pattern: "topicConstants/{topic_constant}"
   };
 
-  // The resource name of the topic constant.
+  // Output only. The resource name of the topic constant.
   // topic constant resource names have the form:
   //
   // `topicConstants/{topic_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/TopicConstant"
+    }
+  ];
 
-  // The ID of the topic.
-  google.protobuf.Int64Value id = 2;
+  // Output only. The ID of the topic.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Resource name of parent of the topic constant.
-  google.protobuf.StringValue topic_constant_parent = 3;
+  // Output only. Resource name of parent of the topic constant.
+  google.protobuf.StringValue topic_constant_parent = 3 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/TopicConstant"
+    }
+  ];
 
-  // The category to target or exclude. Each subsequent element in the array
+  // Output only. The category to target or exclude. Each subsequent element in the array
   // describes a more specific sub-category. For example,
   // {"Pets & Animals", "Pets", "Dogs"} represents the
   // "Pets & Animals/Pets/Dogs" category. List of available topic categories at
   // https://developers.google.com/adwords/api/docs/appendix/verticals
-  repeated google.protobuf.StringValue path = 4;
+  repeated google.protobuf.StringValue path = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/topic_view.proto b/google/ads/googleads/v3/resources/topic_view.proto
index a6903c1b..8f573119 100644
--- a/google/ads/googleads/v3/resources/topic_view.proto
+++ b/google/ads/googleads/v3/resources/topic_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/api/annotations.proto";
 
@@ -37,9 +38,14 @@ message TopicView {
     pattern: "customers/{customer}/topicViews/{topic_view}"
   };
 
-  // The resource name of the topic view.
+  // Output only. The resource name of the topic view.
   // Topic view resource names have the form:
   //
   // `customers/{customer_id}/topicViews/{ad_group_id}~{criterion_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/TopicView"
+    }
+  ];
 }
diff --git a/google/ads/googleads/v3/resources/user_interest.proto b/google/ads/googleads/v3/resources/user_interest.proto
index cf3e8075..8ab8e5e5 100644
--- a/google/ads/googleads/v3/resources/user_interest.proto
+++ b/google/ads/googleads/v3/resources/user_interest.proto
@@ -18,6 +18,7 @@ package google.ads.googleads.v3.resources;
 
 import "google/ads/googleads/v3/common/criterion_category_availability.proto";
 import "google/ads/googleads/v3/enums/user_interest_taxonomy_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -40,27 +41,37 @@ message UserInterest {
     pattern: "customers/{customer}/userInterests/{user_interest}"
   };
 
-  // The resource name of the user interest.
+  // Output only. The resource name of the user interest.
   // User interest resource names have the form:
   //
   // `customers/{customer_id}/userInterests/{user_interest_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/UserInterest"
+    }
+  ];
 
-  // Taxonomy type of the user interest.
-  google.ads.googleads.v3.enums.UserInterestTaxonomyTypeEnum.UserInterestTaxonomyType taxonomy_type = 2;
+  // Output only. Taxonomy type of the user interest.
+  google.ads.googleads.v3.enums.UserInterestTaxonomyTypeEnum.UserInterestTaxonomyType taxonomy_type = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The ID of the user interest.
-  google.protobuf.Int64Value user_interest_id = 3;
+  // Output only. The ID of the user interest.
+  google.protobuf.Int64Value user_interest_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The name of the user interest.
-  google.protobuf.StringValue name = 4;
+  // Output only. The name of the user interest.
+  google.protobuf.StringValue name = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The parent of the user interest.
-  google.protobuf.StringValue user_interest_parent = 5;
+  // Output only. The parent of the user interest.
+  google.protobuf.StringValue user_interest_parent = 5 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/UserInterest"
+    }
+  ];
 
-  // True if the user interest is launched to all channels and locales.
-  google.protobuf.BoolValue launched_to_all = 6;
+  // Output only. True if the user interest is launched to all channels and locales.
+  google.protobuf.BoolValue launched_to_all = 6 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Availability information of the user interest.
-  repeated google.ads.googleads.v3.common.CriterionCategoryAvailability availabilities = 7;
+  // Output only. Availability information of the user interest.
+  repeated google.ads.googleads.v3.common.CriterionCategoryAvailability availabilities = 7 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/user_list.proto b/google/ads/googleads/v3/resources/user_list.proto
index 935881f7..c62da5dc 100644
--- a/google/ads/googleads/v3/resources/user_list.proto
+++ b/google/ads/googleads/v3/resources/user_list.proto
@@ -23,6 +23,7 @@ import "google/ads/googleads/v3/enums/user_list_closing_reason.proto";
 import "google/ads/googleads/v3/enums/user_list_membership_status.proto";
 import "google/ads/googleads/v3/enums/user_list_size_range.proto";
 import "google/ads/googleads/v3/enums/user_list_type.proto";
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -45,21 +46,26 @@ message UserList {
     pattern: "customers/{customer}/userLists/{user_list}"
   };
 
-  // The resource name of the user list.
+  // Immutable. The resource name of the user list.
   // User list resource names have the form:
   //
   // `customers/{customer_id}/userLists/{user_list_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = IMMUTABLE,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/UserList"
+    }
+  ];
 
-  // Id of the user list.
-  google.protobuf.Int64Value id = 2;
+  // Output only. Id of the user list.
+  google.protobuf.Int64Value id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // A flag that indicates if a user may edit a list. Depends on the list
+  // Output only. A flag that indicates if a user may edit a list. Depends on the list
   // ownership and list type. For example, external remarketing user lists are
   // not editable.
   //
   // This field is read-only.
-  google.protobuf.BoolValue read_only = 3;
+  google.protobuf.BoolValue read_only = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Name of this user list. Depending on its access_reason, the user list name
   // may not be unique (e.g. if access_reason=SHARED)
@@ -85,45 +91,45 @@ message UserList {
   // It'll be ignored for logical_user_list.
   google.protobuf.Int64Value membership_life_span = 8;
 
-  // Estimated number of users in this user list, on the Google Display Network.
+  // Output only. Estimated number of users in this user list, on the Google Display Network.
   // This value is null if the number of users has not yet been determined.
   //
   // This field is read-only.
-  google.protobuf.Int64Value size_for_display = 9;
+  google.protobuf.Int64Value size_for_display = 9 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Size range in terms of number of users of the UserList, on the Google
+  // Output only. Size range in terms of number of users of the UserList, on the Google
   // Display Network.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.UserListSizeRangeEnum.UserListSizeRange size_range_for_display = 10;
+  google.ads.googleads.v3.enums.UserListSizeRangeEnum.UserListSizeRange size_range_for_display = 10 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Estimated number of users in this user list in the google.com domain.
+  // Output only. Estimated number of users in this user list in the google.com domain.
   // These are the users available for targeting in Search campaigns.
   // This value is null if the number of users has not yet been determined.
   //
   // This field is read-only.
-  google.protobuf.Int64Value size_for_search = 11;
+  google.protobuf.Int64Value size_for_search = 11 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Size range in terms of number of users of the UserList, for Search ads.
+  // Output only. Size range in terms of number of users of the UserList, for Search ads.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.UserListSizeRangeEnum.UserListSizeRange size_range_for_search = 12;
+  google.ads.googleads.v3.enums.UserListSizeRangeEnum.UserListSizeRange size_range_for_search = 12 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Type of this list.
+  // Output only. Type of this list.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.UserListTypeEnum.UserListType type = 13;
+  google.ads.googleads.v3.enums.UserListTypeEnum.UserListType type = 13 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Indicating the reason why this user list membership status is closed. It is
   // only populated on lists that were automatically closed due to inactivity,
   // and will be cleared once the list membership status becomes open.
   google.ads.googleads.v3.enums.UserListClosingReasonEnum.UserListClosingReason closing_reason = 14;
 
-  // Indicates the reason this account has been granted access to the list.
+  // Output only. Indicates the reason this account has been granted access to the list.
   // The reason can be SHARED, OWNED, LICENSED or SUBSCRIBED.
   //
   // This field is read-only.
-  google.ads.googleads.v3.enums.AccessReasonEnum.AccessReason access_reason = 15;
+  google.ads.googleads.v3.enums.AccessReasonEnum.AccessReason access_reason = 15 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Indicates if this share is still enabled. When a UserList is shared with
   // the user this field is set to ENABLED. Later the userList owner can decide
@@ -134,10 +140,10 @@ message UserList {
   // Indicates if this user list is eligible for Google Search Network.
   google.protobuf.BoolValue eligible_for_search = 17;
 
-  // Indicates this user list is eligible for Google Display Network.
+  // Output only. Indicates this user list is eligible for Google Display Network.
   //
   // This field is read-only.
-  google.protobuf.BoolValue eligible_for_display = 18;
+  google.protobuf.BoolValue eligible_for_display = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The user list.
   //
@@ -146,9 +152,9 @@ message UserList {
     // User list of CRM users provided by the advertiser.
     google.ads.googleads.v3.common.CrmBasedUserListInfo crm_based_user_list = 19;
 
-    // User list which are similar to users from another UserList.
+    // Output only. User list which are similar to users from another UserList.
     // These lists are readonly and automatically created by google.
-    google.ads.googleads.v3.common.SimilarUserListInfo similar_user_list = 20;
+    google.ads.googleads.v3.common.SimilarUserListInfo similar_user_list = 20 [(google.api.field_behavior) = OUTPUT_ONLY];
 
     // User list generated by a rule.
     google.ads.googleads.v3.common.RuleBasedUserListInfo rule_based_user_list = 21;
diff --git a/google/ads/googleads/v3/resources/user_location_view.proto b/google/ads/googleads/v3/resources/user_location_view.proto
index 2bf39a67..11519671 100644
--- a/google/ads/googleads/v3/resources/user_location_view.proto
+++ b/google/ads/googleads/v3/resources/user_location_view.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -43,15 +44,20 @@ message UserLocationView {
     pattern: "customers/{customer}/userLocationViews/{user_location_view}"
   };
 
-  // The resource name of the user location view.
+  // Output only. The resource name of the user location view.
   // UserLocation view resource names have the form:
   //
   // `customers/{customer_id}/userLocationViews/{country_criterion_id}~{targeting_location}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/UserLocationView"
+    }
+  ];
 
-  // Criterion Id for the country.
-  google.protobuf.Int64Value country_criterion_id = 2;
+  // Output only. Criterion Id for the country.
+  google.protobuf.Int64Value country_criterion_id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // Indicates whether location was targeted or not.
-  google.protobuf.BoolValue targeting_location = 3;
+  // Output only. Indicates whether location was targeted or not.
+  google.protobuf.BoolValue targeting_location = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/resources/video.proto b/google/ads/googleads/v3/resources/video.proto
index 9fe906c7..5b984c85 100644
--- a/google/ads/googleads/v3/resources/video.proto
+++ b/google/ads/googleads/v3/resources/video.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package google.ads.googleads.v3.resources;
 
+import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/annotations.proto";
@@ -38,21 +39,26 @@ message Video {
     pattern: "customers/{customer}/videos/{video}"
   };
 
-  // The resource name of the video.
+  // Output only. The resource name of the video.
   // Video resource names have the form:
   //
   // `customers/{customer_id}/videos/{video_id}`
-  string resource_name = 1;
+  string resource_name = 1 [
+    (google.api.field_behavior) = OUTPUT_ONLY,
+    (google.api.resource_reference) = {
+      type: "googleads.googleapis.com/Video"
+    }
+  ];
 
-  // The ID of the video.
-  google.protobuf.StringValue id = 2;
+  // Output only. The ID of the video.
+  google.protobuf.StringValue id = 2 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The owner channel id of the video.
-  google.protobuf.StringValue channel_id = 3;
+  // Output only. The owner channel id of the video.
+  google.protobuf.StringValue channel_id = 3 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The duration of the video in milliseconds.
-  google.protobuf.Int64Value duration_millis = 4;
+  // Output only. The duration of the video in milliseconds.
+  google.protobuf.Int64Value duration_millis = 4 [(google.api.field_behavior) = OUTPUT_ONLY];
 
-  // The title of the video.
-  google.protobuf.StringValue title = 5;
+  // Output only. The title of the video.
+  google.protobuf.StringValue title = 5 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
diff --git a/google/ads/googleads/v3/services/campaign_draft_service.proto b/google/ads/googleads/v3/services/campaign_draft_service.proto
index ea7c7b62..24238dd7 100644
--- a/google/ads/googleads/v3/services/campaign_draft_service.proto
+++ b/google/ads/googleads/v3/services/campaign_draft_service.proto
@@ -74,6 +74,7 @@ service CampaignDraftService {
     option (google.api.method_signature) = "campaign_draft";
     option (google.longrunning.operation_info) = {
       response_type: "google.protobuf.Empty"
+      metadata_type: "google.protobuf.Empty"
     };
   }
 
diff --git a/google/ads/googleads/v3/services/campaign_experiment_service.proto b/google/ads/googleads/v3/services/campaign_experiment_service.proto
index c0aac59b..ba345ae3 100644
--- a/google/ads/googleads/v3/services/campaign_experiment_service.proto
+++ b/google/ads/googleads/v3/services/campaign_experiment_service.proto
@@ -112,6 +112,7 @@ service CampaignExperimentService {
     option (google.api.method_signature) = "campaign_experiment";
     option (google.longrunning.operation_info) = {
       response_type: "google.protobuf.Empty"
+      metadata_type: "google.protobuf.Empty"
     };
   }
 
diff --git a/google/ads/googleads/v3/services/keyword_plan_idea_service.proto b/google/ads/googleads/v3/services/keyword_plan_idea_service.proto
index b2d7dfb5..b14ebdc4 100644
--- a/google/ads/googleads/v3/services/keyword_plan_idea_service.proto
+++ b/google/ads/googleads/v3/services/keyword_plan_idea_service.proto
@@ -19,6 +19,7 @@ package google.ads.googleads.v3.services;
 import "google/ads/googleads/v3/common/keyword_plan_common.proto";
 import "google/ads/googleads/v3/enums/keyword_plan_network.proto";
 import "google/api/annotations.proto";
+import "google/api/field_behavior.proto";
 import "google/protobuf/wrappers.proto";
 import "google/api/client.proto";
 
@@ -51,9 +52,9 @@ message GenerateKeywordIdeasRequest {
   // The ID of the customer with the recommendation.
   string customer_id = 1;
 
-  // The resource name of the language to target.
+  // Required. The resource name of the language to target.
   // Required
-  google.protobuf.StringValue language = 7;
+  google.protobuf.StringValue language = 7 [(google.api.field_behavior) = REQUIRED];
 
   // The resource names of the location to target.
   // Max 10