diff --git a/google/api/annotations.proto b/google/api/annotations.proto
index cbd18b84..3dc23a3e 100644
--- a/google/api/annotations.proto
+++ b/google/api/annotations.proto
@@ -22,6 +22,7 @@ import "google/protobuf/descriptor.proto";
 option java_multiple_files = true;
 option java_outer_classname = "AnnotationsProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 extend google.protobuf.MethodOptions {
   // See `HttpRule`.
diff --git a/google/api/auth.proto b/google/api/auth.proto
index 32d03613..62d05654 100644
--- a/google/api/auth.proto
+++ b/google/api/auth.proto
@@ -21,6 +21,7 @@ import "google/api/annotations.proto";
 option java_multiple_files = true;
 option java_outer_classname = "AuthProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // `Authentication` defines the authentication configuration for an API.
@@ -38,7 +39,9 @@ option java_package = "com.google.api";
 //         oauth:
 //           canonical_scopes: https://www.googleapis.com/auth/calendar.read
 message Authentication {
-  // Individual rules for authentication.
+  // A list of authentication rules that apply to individual API methods.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated AuthenticationRule rules = 3;
 
   // Defines a set of authentication providers that a service supports.
@@ -54,7 +57,6 @@ message Authentication {
 //
 // If a method doesn't have any auth requirements, request credentials will be
 // ignored.
-//
 message AuthenticationRule {
   // Selects the methods to which this rule applies.
   //
@@ -64,9 +66,13 @@ message AuthenticationRule {
   // The requirements for OAuth credentials.
   OAuthRequirements oauth = 2;
 
-  // Whether to allow requests without a credential.  If quota is enabled, an
-  // API key is required for such request to pass the quota check.
+  // Whether to allow requests without a credential. The credential can be
+  // an OAuth token, Google cookies (first-party auth) or EndUserCreds.
   //
+  // For requests without credentials, if the service control environment is
+  // specified, each incoming request **must** be associated with a service
+  // consumer. This can be done by passing an API key that belongs to a consumer
+  // project.
   bool allow_without_credential = 5;
 
   // Requirements for additional authentication providers.
@@ -120,7 +126,6 @@ message AuthProvider {
 // Please note that even though each of the canonical scopes is enough for a
 // request to be accepted and passed to the backend, a request can still fail
 // due to the backend requiring additional scopes or permissions.
-//
 message OAuthRequirements {
   // The list of publicly documented OAuth scopes that are allowed access. An
   // OAuth token containing any of these scopes will be accepted.
diff --git a/google/api/backend.proto b/google/api/backend.proto
index 0d4019c9..3c12c8c3 100644
--- a/google/api/backend.proto
+++ b/google/api/backend.proto
@@ -19,12 +19,14 @@ package google.api;
 option java_multiple_files = true;
 option java_outer_classname = "BackendProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // `Backend` defines the backend configuration for a service.
 message Backend {
-  // A list of backend rules providing configuration for individual API
-  // elements.
+  // A list of API backend rules that apply to individual API methods.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated BackendRule rules = 1;
 }
 
@@ -36,7 +38,6 @@ message BackendRule {
   string selector = 1;
 
   // The address of the API backend.
-  //
   string address = 2;
 
   // The number of seconds to wait for a response from a request.  The
diff --git a/google/api/context.proto b/google/api/context.proto
index a344f5b6..427524f6 100644
--- a/google/api/context.proto
+++ b/google/api/context.proto
@@ -19,6 +19,7 @@ package google.api;
 option java_multiple_files = true;
 option java_outer_classname = "ContextProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // `Context` defines which contexts an API requests.
@@ -39,7 +40,9 @@ option java_package = "com.google.api";
 // Available context types are defined in package
 // `google.rpc.context`.
 message Context {
-  // List of rules for context, applicable to methods.
+  // A list of RPC context rules that apply to individual API methods.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated ContextRule rules = 1;
 }
 
diff --git a/google/api/control.proto b/google/api/control.proto
index 424c8815..d99b2b08 100644
--- a/google/api/control.proto
+++ b/google/api/control.proto
@@ -19,12 +19,12 @@ package google.api;
 option java_multiple_files = true;
 option java_outer_classname = "ControlProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Selects and configures the service controller used by the service.  The
 // service controller handles features like abuse, quota, billing, logging,
 // monitoring, etc.
-//
 message Control {
   // The service control environment to use. If empty, no control plane
   // feature (like quota and billing) will be enabled.
diff --git a/google/api/documentation.proto b/google/api/documentation.proto
index 26f7d8f5..190f8af5 100644
--- a/google/api/documentation.proto
+++ b/google/api/documentation.proto
@@ -19,6 +19,7 @@ package google.api;
 option java_multiple_files = true;
 option java_outer_classname = "DocumentationProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // `Documentation` provides the information for describing a service.
@@ -86,7 +87,9 @@ message Documentation {
   // The top level pages for the documentation set.
   repeated Page pages = 5;
 
-  // Documentation rules for individual elements of the service.
+  // A list of documentation rules that apply to individual API elements.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated DocumentationRule rules = 3;
 
   // The URL to the root of documentation.
diff --git a/google/api/endpoint.proto b/google/api/endpoint.proto
new file mode 100644
index 00000000..5568918d
--- /dev/null
+++ b/google/api/endpoint.proto
@@ -0,0 +1,89 @@
+// Copyright 2016 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package google.api;
+
+import "google/api/annotations.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "EndpointProto";
+option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
+
+
+// `Endpoint` describes a network endpoint that serves a set of APIs.
+// A service may expose any number of endpoints, and all endpoints share the
+// same service configuration, such as quota configuration and monitoring
+// configuration.
+//
+// Example service configuration:
+//
+//     name: library-example.googleapis.com
+//     endpoints:
+//       # Below entry makes 'google.example.library.v1.Library'
+//       # API be served from endpoint address library-example.googleapis.com.
+//       # It also allows HTTP OPTIONS calls to be passed to the backend, for
+//       # it to decide whether the subsequent cross-origin request is
+//       # allowed to proceed.
+//     - name: library-example.googleapis.com
+//       apis: google.example.library.v1.Library
+//       allow_cors: true
+//       # Below entry makes 'google.example.library.v1.Library'
+//       # API be served from endpoint address
+//       # google.example.library-example.v1.LibraryManager.
+//     - name: library-manager.googleapis.com
+//       apis: google.example.library.v1.LibraryManager
+//       # BNS address for a borg job. Can specify a task by appending
+//       # "/taskId" (e.g. "/0") to the job spec.
+//
+// Example OpenAPI extension for endpoint with allow_cors set to true:
+//
+//     {
+//       "swagger": "2.0",
+//       "info": {
+//         "description": "A simple..."
+//       },
+//       "host": "MY_PROJECT_ID.appspot.com",
+//       "x-google-endpoints": [{
+//         "name": "MY_PROJECT_ID.appspot.com",
+//         "allow_cors": "true"
+//       }]
+//     }
+message Endpoint {
+  // The canonical name of this endpoint.
+  string name = 1;
+
+  // DEPRECATED: This field is no longer supported. Instead of using aliases,
+  // please specify multiple [google.api.Endpoint][google.api.Endpoint] for each of the intented
+  // alias.
+  //
+  // Additional names that this endpoint will be hosted on.
+  repeated string aliases = 2;
+
+  // The list of APIs served by this endpoint.
+  repeated string apis = 3;
+
+  // The list of features enabled on this endpoint.
+  repeated string features = 4;
+
+  // Allowing
+  // [CORS](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing), aka
+  // cross-domain traffic, would allow the backends served from this endpoint to
+  // receive and respond to HTTP OPTIONS requests. The response will be used by
+  // the browser to determine whether the subsequent cross-origin request is
+  // allowed to proceed.
+  bool allow_cors = 5;
+}
diff --git a/google/api/http.proto b/google/api/http.proto
index 67173ab6..ad9406d2 100644
--- a/google/api/http.proto
+++ b/google/api/http.proto
@@ -20,13 +20,16 @@ option cc_enable_arenas = true;
 option java_multiple_files = true;
 option java_outer_classname = "HttpProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Defines the HTTP configuration for a service. It contains a list of
 // [HttpRule][google.api.HttpRule], each specifying the mapping of an RPC method
 // to one or more HTTP REST API methods.
 message Http {
-  // A list of HTTP rules for configuring the HTTP REST API methods.
+  // A list of HTTP configuration rules that apply to individual API methods.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated HttpRule rules = 1;
 }
 
@@ -262,7 +265,8 @@ message HttpRule {
 
   // The name of the request field whose value is mapped to the HTTP body, or
   // `*` for mapping all fields not captured by the path pattern to the HTTP
-  // body. NOTE: the referred field must not be a repeated field.
+  // body. NOTE: the referred field must not be a repeated field and must be
+  // present at the top-level of response message type.
   string body = 7;
 
   // Additional HTTP bindings for the selector. Nested bindings must
diff --git a/google/api/label.proto b/google/api/label.proto
index b3c8807e..fec98121 100644
--- a/google/api/label.proto
+++ b/google/api/label.proto
@@ -16,9 +16,11 @@ syntax = "proto3";
 
 package google.api;
 
+option cc_enable_arenas = true;
 option java_multiple_files = true;
 option java_outer_classname = "LabelProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // A description of a label.
diff --git a/google/api/log.proto b/google/api/log.proto
index 27a92672..9bfd71a6 100644
--- a/google/api/log.proto
+++ b/google/api/log.proto
@@ -21,6 +21,7 @@ import "google/api/label.proto";
 option java_multiple_files = true;
 option java_outer_classname = "LogProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // A description of a log type. Example in YAML format:
diff --git a/google/api/logging.proto b/google/api/logging.proto
index 8708a9ba..8e24ba2a 100644
--- a/google/api/logging.proto
+++ b/google/api/logging.proto
@@ -21,6 +21,7 @@ import "google/api/annotations.proto";
 option java_multiple_files = true;
 option java_outer_classname = "LoggingProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Logging configuration of the service.
@@ -54,7 +55,6 @@ option java_package = "com.google.api";
 //       - monitored_resource: library.googleapis.com/branch
 //         logs:
 //         - library.googleapis.com/activity_history
-//
 message Logging {
   // Configuration of a specific logging destination (the producer project
   // or the consumer project).
diff --git a/google/api/metric.proto b/google/api/metric.proto
index c987df51..e0d08807 100644
--- a/google/api/metric.proto
+++ b/google/api/metric.proto
@@ -21,6 +21,7 @@ import "google/api/label.proto";
 option java_multiple_files = true;
 option java_outer_classname = "MetricProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Defines a metric type and its schema.
@@ -30,14 +31,17 @@ message MetricDescriptor {
     // Do not use this default value.
     METRIC_KIND_UNSPECIFIED = 0;
 
-    // Instantaneous measurements of a varying quantity.
+    // An instantaneous measurement of a value.
     GAUGE = 1;
 
-    // Changes over non-overlapping time intervals.
+    // The change in a value during a time interval.
     DELTA = 2;
 
-    // Cumulative value over time intervals that can overlap.
-    // The overlapping intervals must have the same start time.
+    // A value accumulated over a time interval.  Cumulative
+    // measurements in a time series should have the same start time
+    // and increasing end times, until an event resets the cumulative
+    // value to zero and sets a new start time for the following
+    // points.
     CUMULATIVE = 3;
   }
 
diff --git a/google/api/monitored_resource.proto b/google/api/monitored_resource.proto
index b9590cff..cd911559 100644
--- a/google/api/monitored_resource.proto
+++ b/google/api/monitored_resource.proto
@@ -18,11 +18,12 @@ package google.api;
 
 import "google/api/label.proto";
 
+option cc_enable_arenas = true;
 option java_multiple_files = true;
 option java_outer_classname = "MonitoredResourceProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
-option go_package = "google.golang.org/genproto/googleapis/api/monitoredres";
 
 // An object that describes the schema of a [MonitoredResource][google.api.MonitoredResource] object using a
 // type name and a set of labels.  For example, the monitored resource
@@ -44,10 +45,13 @@ message MonitoredResourceDescriptor {
 
   // Required. The monitored resource type. For example, the type
   // `"cloudsql_database"` represents databases in Google Cloud SQL.
+  // The maximum length of this value is 256 characters.
   string type = 1;
 
   // Optional. A concise name for the monitored resource type that might be
-  // displayed in user interfaces. For example, `"Google Cloud SQL Database"`.
+  // displayed in user interfaces. It should be a Title Cased Noun Phrase,
+  // without any article or other determiners. For example,
+  // `"Google Cloud SQL Database"`.
   string display_name = 2;
 
   // Optional. A detailed description of the monitored resource type that might
@@ -71,7 +75,7 @@ message MonitoredResourceDescriptor {
 // `"instance_id"` and `"zone"`:
 //
 //     { "type": "gce_instance",
-//       "labels": { "instance_id": "my-instance",
+//       "labels": { "instance_id": "12345678901234",
 //                   "zone": "us-central1-a" }}
 message MonitoredResource {
   // Required. The monitored resource type. This field must match
diff --git a/google/api/monitoring.proto b/google/api/monitoring.proto
index 4f941da8..e3105025 100644
--- a/google/api/monitoring.proto
+++ b/google/api/monitoring.proto
@@ -21,6 +21,7 @@ import "google/api/annotations.proto";
 option java_multiple_files = true;
 option java_outer_classname = "MonitoringProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Monitoring configuration of the service.
@@ -60,7 +61,6 @@ option java_package = "com.google.api";
 //         metrics:
 //         - library.googleapis.com/book/returned_count
 //         - library.googleapis.com/book/overdue_count
-//
 message Monitoring {
   // Configuration of a specific monitoring destination (the producer project
   // or the consumer project).
diff --git a/google/api/service.proto b/google/api/service.proto
index 3cebcc69..c8382aca 100644
--- a/google/api/service.proto
+++ b/google/api/service.proto
@@ -19,11 +19,10 @@ package google.api;
 import "google/api/annotations.proto";
 import "google/api/auth.proto";
 import "google/api/backend.proto";
-import "google/api/billing.proto";
-import "google/api/consumer.proto";
 import "google/api/context.proto";
 import "google/api/control.proto";
 import "google/api/documentation.proto";
+import "google/api/endpoint.proto";
 import "google/api/http.proto";
 import "google/api/label.proto";
 import "google/api/log.proto";
@@ -41,6 +40,7 @@ import "google/protobuf/wrappers.proto";
 option java_multiple_files = true;
 option java_outer_classname = "ServiceProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // `Service` is the root object of the configuration schema. It
@@ -128,8 +128,10 @@ message Service {
   // Configuration controlling usage of this service.
   Usage usage = 15;
 
-  // Configuration of per-consumer project properties.
-  ProjectProperties project_properties = 17;
+  // Configuration for network endpoints.  If this is empty, then an endpoint
+  // with the same name as the service is automatically generated to service all
+  // defined APIs.
+  repeated Endpoint endpoints = 18;
 
   // Configuration for the service control plane.
   Control control = 21;
@@ -142,12 +144,8 @@ message Service {
 
   // Defines the monitored resources used by this service. This is required
   // by the [Service.monitoring][google.api.Service.monitoring] and [Service.logging][google.api.Service.logging] configurations.
-  //
   repeated MonitoredResourceDescriptor monitored_resources = 25;
 
-  // Billing configuration of the service.
-  Billing billing = 26;
-
   // Logging configuration of the service.
   Logging logging = 27;
 
diff --git a/google/api/system_parameter.proto b/google/api/system_parameter.proto
index 1e3c6ed9..ebd11039 100644
--- a/google/api/system_parameter.proto
+++ b/google/api/system_parameter.proto
@@ -19,6 +19,7 @@ package google.api;
 option java_multiple_files = true;
 option java_outer_classname = "SystemParameterProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // ### System parameter configuration
@@ -37,7 +38,7 @@ message SystemParameters {
   //
   // Example: define api key and alt name for all methods
   //
-  // SystemParameters
+  // system_parameters
   //   rules:
   //     - selector: "*"
   //       parameters:
@@ -48,7 +49,7 @@ message SystemParameters {
   //
   // Example: define 2 api key names for a specific method.
   //
-  // SystemParameters
+  // system_parameters
   //   rules:
   //     - selector: "/ListShelves"
   //       parameters:
@@ -56,6 +57,8 @@ message SystemParameters {
   //           http_header: Api-Key1
   //         - name: api_key
   //           http_header: Api-Key2
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated SystemParameterRule rules = 1;
 }
 
diff --git a/google/api/usage.proto b/google/api/usage.proto
index aec64bbe..57ff7d0a 100644
--- a/google/api/usage.proto
+++ b/google/api/usage.proto
@@ -16,81 +16,24 @@ syntax = "proto3";
 
 package google.api;
 
+import "google/api/annotations.proto";
+
 option java_multiple_files = true;
 option java_outer_classname = "UsageProto";
 option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
 
 
 // Configuration controlling usage of a service.
 message Usage {
-  // Service access types.
-  //
-  // Access to restricted API features is always controlled by
-  // [visibility][google.api.Visibility], independent of the ServiceAccess type.
-  //
-  enum ServiceAccess {
-    // The service can only be seen/used by users identified in the service's
-    // access control policy.
-    //
-    // If the service has not been whitelisted by your domain administrator
-    // for out-of-org publishing, then this mode will be treated like
-    // ORG_RESTRICTED.
-    RESTRICTED = 0;
-
-    // The service can be seen/used by anyone.
-    //
-    // If the service has not been whitelisted by your domain administrator
-    // for out-of-org publishing, then this mode will be treated like
-    // ORG_PUBLIC.
-    //
-    // The discovery document for the service will also be public and allow
-    // unregistered access.
-    PUBLIC = 1;
-
-    // The service can be seen/used by users identified in the service's
-    // access control policy and they are within the organization that owns the
-    // service.
-    //
-    // Access is further constrained to the group
-    // controlled by the administrator of the project/org that owns the
-    // service.
-    ORG_RESTRICTED = 2;
-
-    // The service can be seen/used by the group of users controlled by the
-    // administrator of the project/org that owns the service.
-    ORG_PUBLIC = 3;
-  }
-
-  // Controls which users can see or activate the service.
-  ServiceAccess service_access = 4;
-
   // Requirements that must be satisfied before a consumer project can use the
   // service. Each requirement is of the form <service.name>/<requirement-id>;
   // for example 'serviceusage.googleapis.com/billing-enabled'.
   repeated string requirements = 1;
 
-  // Services that must be activated in order for this service to be used.
-  // The set of services activated as a result of these relations are all
-  // activated in parallel with no guaranteed order of activation.
-  // Each string is a service name, e.g. `calendar.googleapis.com`.
-  repeated string depends_on_services = 2;
-
-  // Services that must be contacted before a consumer can begin using the
-  // service. Each service will be contacted in sequence, and, if any activation
-  // call fails, the entire activation will fail. Each hook is of the form
-  // <service.name>/<hook-id>, where <hook-id> is optional; for example:
-  // 'robotservice.googleapis.com/default'.
-  repeated string activation_hooks = 3;
-
-  // Services that must be contacted before a consumer can deactivate a
-  // service. Each service will be contacted in sequence, and, if any
-  // deactivation call fails, the entire deactivation will fail. Each hook is
-  // of the form <service.name>/<hook-id>, where <hook-id> is optional; for
-  // example:
-  // 'compute.googleapis.com/'.
-  repeated string deactivation_hooks = 5;
-
-  // Individual rules for configuring usage on selected methods.
+  // A list of usage rules that apply to individual API methods.
+  //
+  // **NOTE:** All service configuration rules follow "last one wins" order.
   repeated UsageRule rules = 6;
 }