diff --git a/google/monitoring/v3/agent.proto b/google/monitoring/v3/agent.proto
new file mode 100644
index 000000000..1406091ef
--- /dev/null
+++ b/google/monitoring/v3/agent.proto
@@ -0,0 +1,90 @@
+// 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.monitoring.v3;
+
+import "google/api/annotations.proto";
+import "google/monitoring/v3/common.proto";
+import "google/protobuf/timestamp.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "AgentProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// A single data point from a `collectd`-based plugin.
+message CollectdValue {
+  // The type of measurement for the data source.
+  enum DataSourceType {
+    // An unspecified data source type.
+    // This corresponds to [google.api.MetricDescriptor.MetricKind.METRIC_KIND_UNSPECIFIED].
+    UNSPECIFIED_DATA_SOURCE_TYPE = 0;
+
+    // An instantaneous measurement of a varying quantity.
+    // This corresponds to [google.api.MetricDescriptor.MetricKind.GAUGE].
+    GAUGE = 1;
+
+    // A cumulative value over time.
+    // This corresponds to [google.api.MetricDescriptor.MetricKind.CUMULATIVE].
+    COUNTER = 2;
+
+    // A rate of change of the measurement.
+    DERIVE = 3;
+
+    // An amount of change since the last measurement interval.
+    // This corresponds to [google.api.MetricDescriptor.MetricKind.DELTA].
+    ABSOLUTE = 4;
+  }
+
+  // The data source for the `collectd` value. For example there are
+  // two data sources for network measurements: `"rx"` and `"tx"`.
+  string data_source_name = 1;
+
+  // The type of measurement.
+  DataSourceType data_source_type = 2;
+
+  // The measurement value.
+  TypedValue value = 3;
+}
+
+// A collection of data points sent from a `collectd`-based plugin.
+// See the `collectd` documentation for more information.
+message CollectdPayload {
+  // The measured values during this time interval.
+  // Each value must have a different `dataSourceName`.
+  repeated CollectdValue values = 1;
+
+  // The start time of the interval.
+  google.protobuf.Timestamp start_time = 2;
+
+  // The end time of the interval.
+  google.protobuf.Timestamp end_time = 3;
+
+  // The name of the plugin. Example: `"disk"`.
+  string plugin = 4;
+
+  // The instance name of the plugin Example: `"hdcl"`.
+  string plugin_instance = 5;
+
+  // The measurement type. Example: `"memory"`.
+  string type = 6;
+
+  // The measurement type instance. Example: `"used"`.
+  string type_instance = 7;
+
+  // The measurement metadata. Example: `"process_id" -> 12345`
+  map<string, TypedValue> metadata = 8;
+}
diff --git a/google/monitoring/v3/agent_service.proto b/google/monitoring/v3/agent_service.proto
new file mode 100644
index 000000000..c2b3294c6
--- /dev/null
+++ b/google/monitoring/v3/agent_service.proto
@@ -0,0 +1,60 @@
+// 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.monitoring.v3;
+
+import "google/api/annotations.proto";
+import "google/api/monitored_resource.proto";
+import "google/monitoring/v3/agent.proto";
+import "google/protobuf/empty.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "AgentServiceProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// The AgentTranslation API allows `collectd`-based agents to
+// write time series data to Cloud Monitoring.
+// See [google.monitoring.v3.MetricService.CreateTimeSeries] instead.
+service AgentTranslationService {
+  // **Stackdriver Monitoring Agent only:** Creates a new time series.
+  //
+  // <aside class="caution">This method is only for use by the Google Monitoring Agent.
+  // Use [projects.timeSeries.create][google.monitoring.v3.MetricService.CreateTimeSeries]
+  // instead.</aside>
+  rpc CreateCollectdTimeSeries(CreateCollectdTimeSeriesRequest) returns (google.protobuf.Empty) {
+    option (google.api.http) = { post: "/v3/{name=projects/*}/collectdTimeSeries", body: "*" };
+  }
+}
+
+// The `CreateCollectdTimeSeries` request.
+message CreateCollectdTimeSeriesRequest {
+  // The project in which to create the time series. The format is
+  // `"projects/PROJECT_ID_OR_NUMBER"`.
+  string name = 5;
+
+  // The monitored resource associated with the time series.
+  google.api.MonitoredResource resource = 2;
+
+  // The version of `collectd` that collected the data. Example: `"5.3.0-192.el6"`.
+  string collectd_version = 3;
+
+  // The `collectd` payloads representing the time series data.
+  // You must not include more than a single point for each
+  // time series, so no two payloads can have the same values
+  // for all of the fields `plugin`, `plugin_instance`, `type`, and `type_instance`.
+  repeated CollectdPayload collectd_payloads = 4;
+}
diff --git a/google/monitoring/v3/common.proto b/google/monitoring/v3/common.proto
new file mode 100644
index 000000000..c512fb996
--- /dev/null
+++ b/google/monitoring/v3/common.proto
@@ -0,0 +1,317 @@
+// 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.monitoring.v3;
+
+import "google/api/distribution.proto";
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "CommonProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// A single strongly-typed value.
+message TypedValue {
+  // The typed value field.
+  oneof value {
+    // A Boolean value: `true` or `false`.
+    bool bool_value = 1;
+
+    // A 64-bit integer. Its range is approximately &plusmn;9.2x10<sup>18</sup>.
+    int64 int64_value = 2;
+
+    // A 64-bit double-precision floating-point number. Its magnitude
+    // is approximately &plusmn;10<sup>&plusmn;300</sup> and it has 16
+    // significant digits of precision.
+    double double_value = 3;
+
+    // A variable-length string value.
+    string string_value = 4;
+
+    // A distribution value.
+    google.api.Distribution distribution_value = 5;
+  }
+}
+
+// A time interval extending from after `startTime` through `endTime`.  If
+// `startTime` is omitted, the interval is the single point in time, `endTime`.
+message TimeInterval {
+  // Required. The end of the interval. The interval includes this
+  // time.
+  google.protobuf.Timestamp end_time = 2;
+
+  // If this value is omitted, the interval is a point in time,
+  // `endTime`.  If `startTime` is present, it must be earlier than
+  // (less than) `endTime`.  The interval begins after
+  // `startTime`&mdash;it does not include `startTime`.
+  google.protobuf.Timestamp start_time = 1;
+}
+
+// Describes how to combine, or aggregate, multiple time series to
+// provide different views of the data.
+// See [Aggregation](/monitoring/api/learn_more#aggregation) for more details.
+message Aggregation {
+  // The Aligner describes how to bring the data points in a single
+  // time series into temporal alignment.
+  enum Aligner {
+    // No alignment. Raw data is returned. Not valid if cross-time
+    // series reduction is requested. The value type of the result is
+    // the same as the value type of the input.
+    ALIGN_NONE = 0;
+
+    // Align and convert to delta metric type. This alignment is valid
+    // for cumulative metrics and delta metrics. Aligning an existing
+    // delta metric to a delta metric requires that the alignment
+    // period be increased. The value type of the result is the same
+    // as the value type of the input.
+    ALIGN_DELTA = 1;
+
+    // Align and convert to a rate. This alignment is valid for
+    // cumulative metrics and delta metrics with numeric values. The output is a
+    // gauge metric with value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_RATE = 2;
+
+    // Align by interpolating between adjacent points around the
+    // period boundary. This alignment is valid for gauge and delta
+    // metrics with numeric values. The value type of the result is the same
+    // as the value type of the input.
+    ALIGN_INTERPOLATE = 3;
+
+    // Align by shifting the oldest data point before the period
+    // boundary to the boundary. This alignment is valid for gauge
+    // metrics. The value type of the result is the same as the
+    // value type of the input.
+    ALIGN_NEXT_OLDER = 4;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the minimum of all data points in the
+    // period. This alignment is valid for gauge and delta metrics with numeric
+    // values. The value type of the result is the same as the value
+    // type of the input.
+    ALIGN_MIN = 10;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the maximum of all data points in the
+    // period. This alignment is valid for gauge and delta metrics with numeric
+    // values. The value type of the result is the same as the value
+    // type of the input.
+    ALIGN_MAX = 11;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the average or arithmetic mean of all
+    // data points in the period. This alignment is valid for gauge and delta
+    // metrics with numeric values. The value type of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_MEAN = 12;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the count of all data points in the
+    // period. This alignment is valid for gauge and delta metrics with numeric
+    // or Boolean values. The value type of the output is
+    // [INT64][google.api.MetricDescriptor.ValueType.INT64].
+    ALIGN_COUNT = 13;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the sum of all data points in the
+    // period. This alignment is valid for gauge and delta metrics with numeric
+    // and distribution values. The value type of the output is the
+    // same as the value type of the input.
+    ALIGN_SUM = 14;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the standard deviation of all data
+    // points in the period. This alignment is valid for gauge and delta metrics
+    // with numeric values. The value type of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_STDDEV = 15;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the count of True-valued data points in the
+    // period. This alignment is valid for gauge metrics with
+    // Boolean values. The value type of the output is
+    // [INT64][google.api.MetricDescriptor.ValueType.INT64].
+    ALIGN_COUNT_TRUE = 16;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the fraction of True-valued data points in the
+    // period. This alignment is valid for gauge metrics with Boolean values.
+    // The output value is in the range [0, 1] and has value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_FRACTION_TRUE = 17;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the 99th percentile of all data
+    // points in the period. This alignment is valid for gauge and delta metrics
+    // with distribution values. The output is a gauge metric with value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_PERCENTILE_99 = 18;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the 95th percentile of all data
+    // points in the period. This alignment is valid for gauge and delta metrics
+    // with distribution values. The output is a gauge metric with value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_PERCENTILE_95 = 19;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the 50th percentile of all data
+    // points in the period. This alignment is valid for gauge and delta metrics
+    // with distribution values. The output is a gauge metric with value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_PERCENTILE_50 = 20;
+
+    // Align time series via aggregation. The resulting data point in
+    // the alignment period is the 5th percentile of all data
+    // points in the period. This alignment is valid for gauge and delta metrics
+    // with distribution values. The output is a gauge metric with value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    ALIGN_PERCENTILE_05 = 21;
+  }
+
+  // A Reducer describes how to aggregate data points from multiple
+  // time series into a single time series.
+  enum Reducer {
+    // No cross-time series reduction. The output of the aligner is
+    // returned.
+    REDUCE_NONE = 0;
+
+    // Reduce by computing the mean across time series for each
+    // alignment period. This reducer is valid for delta and
+    // gauge metrics with numeric or distribution values. The value type of the
+    // output is [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    REDUCE_MEAN = 1;
+
+    // Reduce by computing the minimum across time series for each
+    // alignment period. This reducer is valid for delta and
+    // gauge metrics with numeric values. The value type of the output
+    // is the same as the value type of the input.
+    REDUCE_MIN = 2;
+
+    // Reduce by computing the maximum across time series for each
+    // alignment period. This reducer is valid for delta and
+    // gauge metrics with numeric values. The value type of the output
+    // is the same as the value type of the input.
+    REDUCE_MAX = 3;
+
+    // Reduce by computing the sum across time series for each
+    // alignment period. This reducer is valid for delta and
+    // gauge metrics with numeric and distribution values. The value type of
+    // the output is the same as the value type of the input.
+    REDUCE_SUM = 4;
+
+    // Reduce by computing the standard deviation across time series
+    // for each alignment period. This reducer is valid for delta
+    // and gauge metrics with numeric or distribution values. The value type of
+    // the output is [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    REDUCE_STDDEV = 5;
+
+    // Reduce by computing the count of data points across time series
+    // for each alignment period. This reducer is valid for delta
+    // and gauge metrics of numeric, Boolean, distribution, and string value
+    // type. The value type of the output is
+    // [INT64][google.api.MetricDescriptor.ValueType.INT64].
+    REDUCE_COUNT = 6;
+
+    // Reduce by computing the count of True-valued data points across time
+    // series for each alignment period. This reducer is valid for delta
+    // and gauge metrics of Boolean value type. The value type of
+    // the output is [INT64][google.api.MetricDescriptor.ValueType.INT64].
+    REDUCE_COUNT_TRUE = 7;
+
+    // Reduce by computing the fraction of True-valued data points across time
+    // series for each alignment period. This reducer is valid for delta
+    // and gauge metrics of Boolean value type. The output value is in the
+    // range [0, 1] and has value type
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE].
+    REDUCE_FRACTION_TRUE = 8;
+
+    // Reduce by computing 99th percentile of data points across time series
+    // for each alignment period. This reducer is valid for gauge and delta
+    // metrics of numeric and distribution type. The value of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE]
+    REDUCE_PERCENTILE_99 = 9;
+
+    // Reduce by computing 95th percentile of data points across time series
+    // for each alignment period. This reducer is valid for gauge and delta
+    // metrics of numeric and distribution type. The value of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE]
+    REDUCE_PERCENTILE_95 = 10;
+
+    // Reduce by computing 50th percentile of data points across time series
+    // for each alignment period. This reducer is valid for gauge and delta
+    // metrics of numeric and distribution type. The value of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE]
+    REDUCE_PERCENTILE_50 = 11;
+
+    // Reduce by computing 5th percentile of data points across time series
+    // for each alignment period. This reducer is valid for gauge and delta
+    // metrics of numeric and distribution type. The value of the output is
+    // [DOUBLE][google.api.MetricDescriptor.ValueType.DOUBLE]
+    REDUCE_PERCENTILE_05 = 12;
+  }
+
+  // The alignment period for per-[time series][google.monitoring.v3.TimeSeries]
+  // alignment. If present, `alignmentPeriod` must be at least 60
+  // seconds.  After per-time series alignment, each time series will
+  // contain data points only on the period boundaries. If
+  // `perSeriesAligner` is not specified or equals `ALIGN_NONE`, then
+  // this field is ignored. If `perSeriesAligner` is specified and
+  // does not equal `ALIGN_NONE`, then this field must be defined;
+  // otherwise an error is returned.
+  google.protobuf.Duration alignment_period = 1;
+
+  // The approach to be used to align individual time series. Not all
+  // alignment functions may be applied to all time series, depending
+  // on the metric type and value type of the original time
+  // series. Alignment may change the metric type or the value type of
+  // the time series.
+  //
+  // Time series data must be aligned in order to perform cross-time
+  // series reduction. If `crossSeriesReducer` is specified, then
+  // `perSeriesAligner` must be specified and not equal `ALIGN_NONE`
+  // and `alignmentPeriod` must be specified; otherwise, an error is
+  // returned.
+  Aligner per_series_aligner = 2;
+
+  // The approach to be used to combine time series. Not all reducer
+  // functions may be applied to all time series, depending on the
+  // metric type and the value type of the original time
+  // series. Reduction may change the metric type of value type of the
+  // time series.
+  //
+  // Time series data must be aligned in order to perform cross-time
+  // series reduction. If `crossSeriesReducer` is specified, then
+  // `perSeriesAligner` must be specified and not equal `ALIGN_NONE`
+  // and `alignmentPeriod` must be specified; otherwise, an error is
+  // returned.
+  Reducer cross_series_reducer = 4;
+
+  // The set of fields to preserve when `crossSeriesReducer` is
+  // specified. The `groupByFields` determine how the time series
+  // are partitioned into subsets prior to applying the aggregation
+  // function. Each subset contains time series that have the same
+  // value for each of the grouping fields. Each individual time
+  // series is a member of exactly one subset. The
+  // `crossSeriesReducer` is applied to each subset of time series.
+  // Fields not specified in `groupByFields` are aggregated away.
+  // If `groupByFields` is not specified, the time series are
+  // aggregated into a single output time series. If
+  // `crossSeriesReducer` is not defined, this field is ignored.
+  repeated string group_by_fields = 5;
+}
diff --git a/google/monitoring/v3/group.proto b/google/monitoring/v3/group.proto
new file mode 100644
index 000000000..6050b4d52
--- /dev/null
+++ b/google/monitoring/v3/group.proto
@@ -0,0 +1,74 @@
+// 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.monitoring.v3;
+
+option java_multiple_files = true;
+option java_outer_classname = "GroupProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// The description of a dynamic collection of monitored resources. Each group
+// has a filter that is matched against monitored resources and their associated
+// metadata. If a group's filter matches an available monitored resource, then
+// that resource is a member of that group.  Groups can contain any number of
+// monitored resources, and each monitored resource can be a member of any
+// number of groups.
+//
+// Groups can be nested in parent-child hierarchies. The `parentName` field
+// identifies an optional parent for each group.  If a group has a parent, then
+// the only monitored resources available to be matched by the group's filter
+// are the resources contained in the parent group.  In other words, a group
+// contains the monitored resources that match its filter and the filters of all
+// the group's ancestors.  A group without a parent can contain any monitored
+// resource.
+//
+// For example, consider an infrastructure running a set of instances with two
+// user-defined tags: `"environment"` and `"role"`. A parent group has a filter,
+// `environment="production"`.  A child of that parent group has a filter,
+// `role="transcoder"`.  The parent group contains all instances in the
+// production environment, regardless of their roles.  The child group contains
+// instances that have the transcoder role *and* are in the production
+// environment.
+//
+// The monitored resources contained in a group can change at any moment,
+// depending on what resources exist and what filters are associated with the
+// group and its ancestors.
+message Group {
+  // The name of this group.
+  // The format is
+  // `"projects/{project_id_or_number}/groups/{group_id}"`.
+  // When creating a group, this field is ignored and a new name is created
+  // consisting of the project specified in the call to `CreateGroup`
+  // and a unique `{group_id}` that is generated automatically.
+  // @OutputOnly
+  string name = 1;
+
+  // A user-assigned name for this group, used only for display purposes.
+  string display_name = 2;
+
+  // The name of the group's parent, if it has one.
+  // The format is `"projects/{project_id_or_number}/groups/{group_id}"`.
+  // For groups with no parent, `parentName` is the empty string, `""`.
+  string parent_name = 3;
+
+  // The filter used to determine which monitored resources belong to this group.
+  string filter = 5;
+
+  // If true, the members of this group are considered to be a cluster.
+  // The system can perform additional analysis on groups that are clusters.
+  bool is_cluster = 6;
+}
diff --git a/google/monitoring/v3/group_service.proto b/google/monitoring/v3/group_service.proto
new file mode 100644
index 000000000..2ba981695
--- /dev/null
+++ b/google/monitoring/v3/group_service.proto
@@ -0,0 +1,210 @@
+// 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.monitoring.v3;
+
+import "google/api/annotations.proto";
+import "google/api/monitored_resource.proto";
+import "google/monitoring/v3/common.proto";
+import "google/monitoring/v3/group.proto";
+import "google/protobuf/empty.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "GroupServiceProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// The Group API lets you inspect and manage your
+// [groups](google.monitoring.v3.Group).
+//
+// A group is a named filter that is used to identify
+// a collection of monitored resources. Groups are typically used to
+// mirror the physical and/or logical topology of the environment.
+// Because group membership is computed dynamically, monitored
+// resources that are started in the future are automatically placed
+// in matching groups. By using a group to name monitored resources in,
+// for example, an alert policy, the target of that alert policy is
+// updated automatically as monitored resources are added and removed
+// from the infrastructure.
+service GroupService {
+  // Lists the existing groups. The project ID in the URL path must refer
+  // to a Stackdriver account.
+  rpc ListGroups(ListGroupsRequest) returns (ListGroupsResponse) {
+    option (google.api.http) = { get: "/v3/{name=projects/*}/groups" };
+  }
+
+  // Gets a single group. The project ID in the URL path must refer to a
+  // Stackdriver account.
+  rpc GetGroup(GetGroupRequest) returns (Group) {
+    option (google.api.http) = { get: "/v3/{name=projects/*/groups/*}" };
+  }
+
+  // Creates a new group. The project ID in the URL path must refer to a
+  // Stackdriver account.
+  rpc CreateGroup(CreateGroupRequest) returns (Group) {
+    option (google.api.http) = { post: "/v3/{name=projects/*}/groups", body: "group" };
+  }
+
+  // Updates an existing group.
+  // You can change any group attributes except `name`.
+  // The project ID in the URL path must refer to a Stackdriver account.
+  rpc UpdateGroup(UpdateGroupRequest) returns (Group) {
+    option (google.api.http) = { put: "/v3/{group.name=projects/*/groups/*}", body: "group" };
+  }
+
+  // Deletes an existing group. The project ID in the URL path must refer to a
+  // Stackdriver account.
+  rpc DeleteGroup(DeleteGroupRequest) returns (google.protobuf.Empty) {
+    option (google.api.http) = { delete: "/v3/{name=projects/*/groups/*}" };
+  }
+
+  // Lists the monitored resources that are members of a group. The project ID
+  // in the URL path must refer to a Stackdriver account.
+  rpc ListGroupMembers(ListGroupMembersRequest) returns (ListGroupMembersResponse) {
+    option (google.api.http) = { get: "/v3/{name=projects/*/groups/*}/members" };
+  }
+}
+
+// The `ListGroup` request.
+message ListGroupsRequest {
+  // The project whose groups are to be listed. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 7;
+
+  // An optional filter consisting of a single group name.  The filters limit the
+  // groups returned based on their parent-child relationship with the specified
+  // group. If no filter is specified, all groups are returned.
+  oneof filter {
+    // A group name: `"projects/{project_id_or_number}/groups/{group_id}"`.
+    // Returns groups whose `parentName` field contains the group
+    // name.  If no groups have this parent, the results are empty.
+    string children_of_group = 2;
+
+    // A group name: `"projects/{project_id_or_number}/groups/{group_id}"`.
+    // Returns groups that are ancestors of the specified group.
+    // The groups are returned in order, starting with the immediate parent and
+    // ending with the most distant ancestor.  If the specified group has no
+    // immediate parent, the results are empty.
+    string ancestors_of_group = 3;
+
+    // A group name: `"projects/{project_id_or_number}/groups/{group_id}"`.
+    // Returns the descendants of the specified group.  This is a superset of
+    // the results returned by the `childrenOfGroup` filter, and includes
+    // children-of-children, and so forth.
+    string descendants_of_group = 4;
+  }
+
+  // A positive number that is the maximum number of results to return.
+  int32 page_size = 5;
+
+  // If this field is not empty then it must contain the `nextPageToken` value
+  // returned by a previous call to this method.  Using this field causes the
+  // method to return additional results from the previous method call.
+  string page_token = 6;
+}
+
+// The `ListGroups` response.
+message ListGroupsResponse {
+  // The groups that match the specified filters.
+  repeated Group group = 1;
+
+  // If there are more results than have been returned, then this field is set
+  // to a non-empty value.  To see the additional results,
+  // use that value as `pageToken` in the next call to this method.
+  string next_page_token = 2;
+}
+
+// The `GetGroup` request.
+message GetGroupRequest {
+  // The group to retrieve. The format is
+  // `"projects/{project_id_or_number}/groups/{group_id}"`.
+  string name = 3;
+}
+
+// The `CreateGroup` request.
+message CreateGroupRequest {
+  // The project in which to create the group. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 4;
+
+  // A group definition. It is an error to define the `name` field because
+  // the system assigns the name.
+  Group group = 2;
+
+  // If true, validate this request but do not create the group.
+  bool validate_only = 3;
+}
+
+// The `UpdateGroup` request.
+message UpdateGroupRequest {
+  // The new definition of the group.  All fields of the existing group,
+  // excepting `name`, are replaced with the corresponding fields of this group.
+  Group group = 2;
+
+  // If true, validate this request but do not update the existing group.
+  bool validate_only = 3;
+}
+
+// The `DeleteGroup` request. You can only delete a group if it has no children.
+message DeleteGroupRequest {
+  // The group to delete. The format is
+  // `"projects/{project_id_or_number}/groups/{group_id}"`.
+  string name = 3;
+}
+
+// The `ListGroupMembers` request.
+message ListGroupMembersRequest {
+  // The group whose members are listed. The format is
+  // `"projects/{project_id_or_number}/groups/{group_id}"`.
+  string name = 7;
+
+  // A positive number that is the maximum number of results to return.
+  int32 page_size = 3;
+
+  // If this field is not empty then it must contain the `nextPageToken` value
+  // returned by a previous call to this method.  Using this field causes the
+  // method to return additional results from the previous method call.
+  string page_token = 4;
+
+  // An optional [list filter](/monitoring/api/learn_more#filtering) describing
+  // the members to be returned.  The filter may reference the type, labels, and
+  // metadata of monitored resources that comprise the group.
+  // For example, to return only resources representing Compute Engine VM
+  // instances, use this filter:
+  //
+  //     resource.type = "gce_instance"
+  string filter = 5;
+
+  // An optional time interval for which results should be returned. Only
+  // members that were part of the group during the specified interval are
+  // included in the response.  If no interval is provided then the group
+  // membership over the last minute is returned.
+  TimeInterval interval = 6;
+}
+
+// The `ListGroupMembers` response.
+message ListGroupMembersResponse {
+  // A set of monitored resources in the group.
+  repeated google.api.MonitoredResource members = 1;
+
+  // If there are more results than have been returned, then this field is
+  // set to a non-empty value.  To see the additional results, use that value as
+  // `pageToken` in the next call to this method.
+  string next_page_token = 2;
+
+  // The total number of elements matching this request.
+  int32 total_size = 3;
+}
diff --git a/google/monitoring/v3/metric.proto b/google/monitoring/v3/metric.proto
new file mode 100644
index 000000000..d38b3ac24
--- /dev/null
+++ b/google/monitoring/v3/metric.proto
@@ -0,0 +1,65 @@
+// 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.monitoring.v3;
+
+import "google/api/metric.proto";
+import "google/api/monitored_resource.proto";
+import "google/monitoring/v3/common.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "MetricProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// A single data point in a time series.
+message Point {
+  // The time interval to which the value applies.
+  TimeInterval interval = 1;
+
+  // The value of the data point.
+  TypedValue value = 2;
+}
+
+// A collection of data points that describes the time-varying nature
+// of a metric. A time series is identified by a combination of a
+// fully-specified monitored resource and a fully-specified metric.
+message TimeSeries {
+  // The fully-specified metric used to identify the time series.
+  google.api.Metric metric = 1;
+
+  // The fully-specified monitored resource used to identify the time series.
+  google.api.MonitoredResource resource = 2;
+
+  // The metric kind of the time series. This can be different than the metric
+  // kind specified in [google.api.MetricDescriptor] because of alignment and
+  // reduction operations on the data. This field is ignored when writing data;
+  // the value specified in the descriptor is used instead.
+  // @OutputOnly
+  google.api.MetricDescriptor.MetricKind metric_kind = 3;
+
+  // The value type of the time series. This can be different than the value
+  // type specified in [google.api.MetricDescriptor] because of alignment and
+  // reduction operations on the data. This field is ignored when writing data;
+  // the value specified in the descriptor is used instead.
+  // @OutputOnly
+  google.api.MetricDescriptor.ValueType value_type = 4;
+
+  // The data points of this time series. When used as output, points will be
+  // sorted by decreasing time order. When used as input, points could be
+  // written in any orders.
+  repeated Point points = 5;
+}
diff --git a/google/monitoring/v3/metric_service.proto b/google/monitoring/v3/metric_service.proto
new file mode 100644
index 000000000..9eba148d8
--- /dev/null
+++ b/google/monitoring/v3/metric_service.proto
@@ -0,0 +1,284 @@
+// 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.monitoring.v3;
+
+import "google/api/annotations.proto";
+import "google/api/metric.proto";
+import "google/api/monitored_resource.proto";
+import "google/monitoring/v3/common.proto";
+import "google/monitoring/v3/metric.proto";
+import "google/protobuf/empty.proto";
+import "google/rpc/status.proto";
+
+option java_multiple_files = true;
+option java_outer_classname = "MetricServiceProto";
+option java_package = "com.google.monitoring.v3";
+
+
+// Manages metric descriptors, monitored resource descriptors, and
+// time series data.
+service MetricService {
+  // Lists monitored resource descriptors that match a filter.
+  rpc ListMonitoredResourceDescriptors(ListMonitoredResourceDescriptorsRequest) returns (ListMonitoredResourceDescriptorsResponse) {
+    option (google.api.http) = { get: "/v3/{name=projects/*}/monitoredResourceDescriptors" };
+  }
+
+  // Gets a single monitored resource descriptor.
+  rpc GetMonitoredResourceDescriptor(GetMonitoredResourceDescriptorRequest) returns (google.api.MonitoredResourceDescriptor) {
+    option (google.api.http) = { get: "/v3/{name=projects/*/monitoredResourceDescriptors/*}" };
+  }
+
+  // Lists metric descriptors that match a filter.
+  rpc ListMetricDescriptors(ListMetricDescriptorsRequest) returns (ListMetricDescriptorsResponse) {
+    option (google.api.http) = { get: "/v3/{name=projects/*}/metricDescriptors" };
+  }
+
+  // Gets a single metric descriptor.
+  rpc GetMetricDescriptor(GetMetricDescriptorRequest) returns (google.api.MetricDescriptor) {
+    option (google.api.http) = { get: "/v3/{name=projects/*/metricDescriptors/**}" };
+  }
+
+  // Creates a new metric descriptor.
+  // User-created metric descriptors define
+  // [custom metrics](/monitoring/custom-metrics).
+  rpc CreateMetricDescriptor(CreateMetricDescriptorRequest) returns (google.api.MetricDescriptor) {
+    option (google.api.http) = { post: "/v3/{name=projects/*}/metricDescriptors", body: "metric_descriptor" };
+  }
+
+  // Deletes a metric descriptor. Only user-created
+  // [custom metrics](/monitoring/custom-metrics) can be deleted.
+  rpc DeleteMetricDescriptor(DeleteMetricDescriptorRequest) returns (google.protobuf.Empty) {
+    option (google.api.http) = { delete: "/v3/{name=projects/*/metricDescriptors/**}" };
+  }
+
+  // Lists time series that match a filter.
+  rpc ListTimeSeries(ListTimeSeriesRequest) returns (ListTimeSeriesResponse) {
+    option (google.api.http) = { get: "/v3/{name=projects/*}/timeSeries" };
+  }
+
+  // Creates or adds data to one or more time series.
+  // The response is empty if all time series in the request were written.
+  // If any time series could not be written, a corresponding failure message is
+  // included in the error response.
+  rpc CreateTimeSeries(CreateTimeSeriesRequest) returns (google.protobuf.Empty) {
+    option (google.api.http) = { post: "/v3/{name=projects/*}/timeSeries", body: "*" };
+  }
+}
+
+// The `ListMonitoredResourceDescriptors` request.
+message ListMonitoredResourceDescriptorsRequest {
+  // The project on which to execute the request. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 5;
+
+  // An optional [filter](/monitoring/api/v3/filters) describing
+  // the descriptors to be returned.  The filter can reference
+  // the descriptor's type and labels. For example, the
+  // following filter returns only Google Compute Engine descriptors
+  // that have an `id` label:
+  //
+  //     resource.type = starts_with("gce_") AND resource.label:id
+  string filter = 2;
+
+  // A positive number that is the maximum number of results to return.
+  int32 page_size = 3;
+
+  // If this field is not empty then it must contain the `nextPageToken` value
+  // returned by a previous call to this method.  Using this field causes the
+  // method to return additional results from the previous method call.
+  string page_token = 4;
+}
+
+// The `ListMonitoredResourcDescriptors` response.
+message ListMonitoredResourceDescriptorsResponse {
+  // The monitored resource descriptors that are available to this project
+  // and that match `filter`, if present.
+  repeated google.api.MonitoredResourceDescriptor resource_descriptors = 1;
+
+  // If there are more results than have been returned, then this field is set
+  // to a non-empty value.  To see the additional results,
+  // use that value as `pageToken` in the next call to this method.
+  string next_page_token = 2;
+}
+
+// The `GetMonitoredResourceDescriptor` request.
+message GetMonitoredResourceDescriptorRequest {
+  // The monitored resource descriptor to get.  The format is
+  // `"projects/{project_id_or_number}/monitoredResourceDescriptors/{resource_type}"`.
+  // The `{resource_type}` is a predefined type, such as
+  // `cloudsql_database`.
+  string name = 3;
+}
+
+// The `ListMetricDescriptors` request.
+message ListMetricDescriptorsRequest {
+  // The project on which to execute the request. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 5;
+
+  // If this field is empty, all custom and
+  // system-defined metric descriptors are returned.
+  // Otherwise, the [filter](/monitoring/api/v3/filters)
+  // specifies which metric descriptors are to be
+  // returned. For example, the following filter matches all
+  // [custom metrics](/monitoring/custom-metrics):
+  //
+  //     metric.type = starts_with("custom.googleapis.com/")
+  string filter = 2;
+
+  // A positive number that is the maximum number of results to return.
+  int32 page_size = 3;
+
+  // If this field is not empty then it must contain the `nextPageToken` value
+  // returned by a previous call to this method.  Using this field causes the
+  // method to return additional results from the previous method call.
+  string page_token = 4;
+}
+
+// The `ListMetricDescriptors` response.
+message ListMetricDescriptorsResponse {
+  // The metric descriptors that are available to the project
+  // and that match the value of `filter`, if present.
+  repeated google.api.MetricDescriptor metric_descriptors = 1;
+
+  // If there are more results than have been returned, then this field is set
+  // to a non-empty value.  To see the additional results,
+  // use that value as `pageToken` in the next call to this method.
+  string next_page_token = 2;
+}
+
+// The `GetMetricDescriptor` request.
+message GetMetricDescriptorRequest {
+  // The metric descriptor on which to execute the request. The format is
+  // `"projects/{project_id_or_number}/metricDescriptors/{metric_id}"`.
+  // An example value of `{metric_id}` is
+  // `"compute.googleapis.com/instance/disk/read_bytes_count"`.
+  string name = 3;
+}
+
+// The `CreateMetricDescriptor` request.
+message CreateMetricDescriptorRequest {
+  // The project on which to execute the request. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 3;
+
+  // The new [custom metric](/monitoring/custom-metrics)
+  // descriptor.
+  google.api.MetricDescriptor metric_descriptor = 2;
+}
+
+// The `DeleteMetricDescriptor` request.
+message DeleteMetricDescriptorRequest {
+  // The metric descriptor on which to execute the request. The format is
+  // `"projects/{project_id_or_number}/metricDescriptors/{metric_id}"`.
+  // An example of `{metric_id}` is:
+  // `"custom.googleapis.com/my_test_metric"`.
+  string name = 3;
+}
+
+// The `ListTimeSeries` request.
+message ListTimeSeriesRequest {
+  // Controls which fields are returned by `ListTimeSeries`.
+  enum TimeSeriesView {
+    // Returns the identity of the metric(s), the time series,
+    // and the time series data.
+    FULL = 0;
+
+    // Returns the identity of the metric and the time series resource,
+    // but not the time series data.
+    HEADERS = 1;
+  }
+
+  // The project on which to execute the request. The format is
+  // "projects/{project_id_or_number}".
+  string name = 10;
+
+  // A [monitoring filter](/monitoring/api/v3/filters) that specifies which time
+  // series should be returned.  The filter must specify a single metric type,
+  // and can additionally specify metric labels and other information. For
+  // example:
+  //
+  //     metric.type = "compute.googleapis.com/instance/cpu/usage_time" AND
+  //         metric.label.instance_name = "my-instance-name"
+  string filter = 2;
+
+  // The time interval for which results should be returned. Only time series
+  // that contain data points in the specified interval are included
+  // in the response.
+  TimeInterval interval = 4;
+
+  // By default, the raw time series data is returned.
+  // Use this field to combine multiple time series for different
+  // views of the data.
+  Aggregation aggregation = 5;
+
+  // Specifies the order in which the points of the time series should
+  // be returned.  By default, results are not ordered.  Currently,
+  // this field must be left blank.
+  string order_by = 6;
+
+  // Specifies which information is returned about the time series.
+  TimeSeriesView view = 7;
+
+  // A positive number that is the maximum number of results to return.
+  // When `view` field sets to `FULL`, it limits the number of `Points` server
+  // will return; if `view` field is `HEADERS`, it limits the number of
+  // `TimeSeries` server will return.
+  int32 page_size = 8;
+
+  // If this field is not empty then it must contain the `nextPageToken` value
+  // returned by a previous call to this method.  Using this field causes the
+  // method to return additional results from the previous method call.
+  string page_token = 9;
+}
+
+// The `ListTimeSeries` response.
+message ListTimeSeriesResponse {
+  // One or more time series that match the filter included in the request.
+  repeated TimeSeries time_series = 1;
+
+  // If there are more results than have been returned, then this field is set
+  // to a non-empty value.  To see the additional results,
+  // use that value as `pageToken` in the next call to this method.
+  string next_page_token = 2;
+}
+
+// The `CreateTimeSeries` request.
+message CreateTimeSeriesRequest {
+  // The project on which to execute the request. The format is
+  // `"projects/{project_id_or_number}"`.
+  string name = 3;
+
+  // The new data to be added to a list of time series.
+  // Adds at most one data point to each of several time series.  The new data
+  // point must be more recent than any other point in its time series.  Each
+  // `TimeSeries` value must fully specify a unique time series by supplying
+  // all label values for the metric and the monitored resource.
+  repeated TimeSeries time_series = 2;
+}
+
+// Describes the result of a failed request to write data to a time series.
+message CreateTimeSeriesError {
+  // The time series, including the `Metric`, `MonitoredResource`,
+  // and `Point`s (including timestamp and value) that resulted
+  // in the error. This field provides all of the context that
+  // would be needed to retry the operation.
+  TimeSeries time_series = 1;
+
+  // The status of the requested write operation.
+  google.rpc.Status status = 2;
+}