diff --git a/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqExtensions.cs b/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqExtensions.cs
index 127c6a0554..12732395c0 100644
--- a/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqExtensions.cs
+++ b/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqExtensions.cs
@@ -612,6 +612,27 @@ public static FeedIterator ToStreamIterator<T>(this IQueryable<T> query)
             return linqQuery.ToStreamIterator();
         }
 
+        /// <summary>
+        /// This extension method returns the Index Metrics for a given Response object. The index utilization metrics is to be used for debugging purposes only. 
+        /// This result is only available if QueryRequestOptions.PopulateIndexMetrics is set to true.Returns null if the index metrics is not available in the response.
+        /// </summary>
+        /// <param name="response">The query Response.</param>
+        /// <returns>A string represents the Index Metrics.</returns>
+        /// <example>
+        /// This example shows a common usage of this function.
+        /// <code language="c#">
+        /// <![CDATA[
+        /// QueryRequestOptions queryRequestOption = new QueryRequestOptions() { PopulateIndexMetrics = true };
+        /// Response<int> response = await this.Container.GetLinqQueryable<T>(requestOptions: queryRequestOption).Select(item => item.Id).CountAsync(cancellationToken);
+        /// string indexMetrics = response.GetIndexMetrics();
+        /// ]]>
+        /// </code>
+        /// </example>
+        public static string GetIndexMetrics<T>(this Response<T> response)
+        {
+            return ResponseMessage.DecodeIndexMetrics(response.Headers, isBase64Encoded: false)?.Value;
+        }
+
         /// <summary>
         /// Returns the maximum value in a generic <see cref="IQueryable{TSource}" />.
         /// </summary>
diff --git a/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqQuery.cs b/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqQuery.cs
index 6676d096c9..136e0d3ba0 100644
--- a/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqQuery.cs
+++ b/Microsoft.Azure.Cosmos/src/Linq/CosmosLinqQuery.cs
@@ -215,6 +215,18 @@ internal async Task<Response<T>> AggregateResultAsync(CancellationToken cancella
                 {
                     FeedResponse<T> response = await localFeedIterator.ReadNextAsync(rootTrace, cancellationToken);
                     headers.RequestCharge += response.RequestCharge;
+
+                    // IndexMetrics only show up on first round trip
+                    if (response.Headers.IndexUtilizationText != null)
+                    {
+                        headers.IndexUtilizationText = response.Headers.IndexUtilizationText;
+                    }
+
+                    if (response.Headers.ActivityId != null && headers.ActivityId == null)
+                    {
+                        headers.ActivityId = response.Headers.ActivityId;
+                    }
+
                     result.AddRange(response);
                 }
             }
diff --git a/Microsoft.Azure.Cosmos/src/Query/Core/Pipeline/Aggregate/AggregateQueryPipelineStage.cs b/Microsoft.Azure.Cosmos/src/Query/Core/Pipeline/Aggregate/AggregateQueryPipelineStage.cs
index 13c245c4b3..1fe3fc4fa6 100644
--- a/Microsoft.Azure.Cosmos/src/Query/Core/Pipeline/Aggregate/AggregateQueryPipelineStage.cs
+++ b/Microsoft.Azure.Cosmos/src/Query/Core/Pipeline/Aggregate/AggregateQueryPipelineStage.cs
@@ -71,7 +71,8 @@ public override async ValueTask<bool> MoveNextAsync(ITrace trace, CancellationTo
 
             double requestCharge = 0;
             IReadOnlyDictionary<string, string> cumulativeAdditionalHeaders = default;
-
+
+            string activityId = default;
             while (await this.inputStage.MoveNextAsync(trace, cancellationToken))
             {
                 TryCatch<QueryPage> tryGetPageFromSource = this.inputStage.Current;
@@ -82,6 +83,12 @@ public override async ValueTask<bool> MoveNextAsync(ITrace trace, CancellationTo
                 }
 
                 QueryPage sourcePage = tryGetPageFromSource.Result;
+
+                if (activityId == default && sourcePage.ActivityId != default)
+                {
+                    // We only take the first activityId.
+                    activityId = sourcePage.ActivityId;
+                }
 
                 requestCharge += sourcePage.RequestCharge;
 
@@ -110,7 +117,7 @@ public override async ValueTask<bool> MoveNextAsync(ITrace trace, CancellationTo
             QueryPage queryPage = new QueryPage(
                 documents: finalResult,
                 requestCharge: requestCharge,
-                activityId: default,
+                activityId: activityId,
                 cosmosQueryExecutionInfo: default,
                 distributionPlanSpec: default,
                 disallowContinuationTokenMessage: default,
diff --git a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/CosmosItemLinqTests.cs b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/Linq/CosmosItemLinqTests.cs
similarity index 96%
rename from Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/CosmosItemLinqTests.cs
rename to Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/Linq/CosmosItemLinqTests.cs
index 9f1b8c2177..846739cf98 100644
--- a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/CosmosItemLinqTests.cs
+++ b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/Linq/CosmosItemLinqTests.cs
@@ -313,7 +313,7 @@ public async Task QueryableExtentionFunctionsTest()
             //Creating items for query.
             IList<ToDoActivity> itemList = await ToDoActivity.CreateRandomItems(container: this.Container, pkCount: 10, perPKItemCount: 1, randomPartitionKey: true);
 
-            QueryRequestOptions queryRequestOptions = new QueryRequestOptions();
+            QueryRequestOptions queryRequestOptions = new QueryRequestOptions() { PopulateIndexMetrics = true };
             IOrderedQueryable<ToDoActivity> linqQueryable = this.Container.GetItemLinqQueryable<ToDoActivity>(
                 requestOptions: queryRequestOptions);
 
@@ -396,6 +396,34 @@ public async Task QueryableExtentionFunctionsTest()
             Assert.AreEqual(100, maxTaskNum);
         }
 
+
+        [TestMethod]
+        public async Task GetIndexMetricsTest()
+        {
+            //Creating items for query.
+            IList<ToDoActivity> itemList = await ToDoActivity.CreateRandomItems(container: this.Container, pkCount: 10, perPKItemCount: 1, randomPartitionKey: true);
+
+            QueryRequestOptions queryRequestOptions = new QueryRequestOptions() { PopulateIndexMetrics = true };
+            IOrderedQueryable<ToDoActivity> linqQueryable = this.Container.GetItemLinqQueryable<ToDoActivity>(
+                requestOptions: queryRequestOptions);
+
+            // Response object with valid index metrics field
+            Response<int> response = await linqQueryable.Select(item => item.taskNum).SumAsync();
+            this.VerifyResponse(response, 420, queryRequestOptions);
+
+            string indexMetrics = response.GetIndexMetrics();
+            Assert.AreEqual(
+                @"{""UtilizedIndexes"":{""SingleIndexes"":[{""IndexSpec"":""/taskNum/?""}],""CompositeIndexes"":[]},""PotentialIndexes"":{""SingleIndexes"":[],""CompositeIndexes"":[]}}",
+                indexMetrics);
+
+            // Response object with null index metrics field
+            response.Headers.IndexUtilizationText = null;
+            indexMetrics = response.GetIndexMetrics();
+            Assert.AreEqual(
+                null,
+                indexMetrics);
+        }
+
         [DataRow(false)]
         [DataRow(true)]
         [TestMethod]
@@ -1012,6 +1040,9 @@ private void VerifyResponse<T>(
         {
             Assert.AreEqual<T>(expectedValue, response.Resource);
             Assert.IsTrue(response.RequestCharge > 0);
+            Assert.IsNotNull(response.Headers.IndexUtilizationText);
+            Assert.IsNotNull(response.Headers.ActivityId);
+            Assert.IsNotNull(response.ActivityId);
         }
     }
 }
diff --git a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Contracts/DotNetSDKAPI.json b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Contracts/DotNetSDKAPI.json
index 80efed4ee2..7f177160fa 100644
--- a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Contracts/DotNetSDKAPI.json
+++ b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Contracts/DotNetSDKAPI.json
@@ -6437,6 +6437,13 @@
           ],
           "MethodInfo": "System.Linq.IOrderedQueryable`1[TSource] OrderByRank[TSource,TKey](System.Linq.IQueryable`1[TSource], System.Linq.Expressions.Expression`1[System.Func`2[TSource,TKey]]);IsAbstract:False;IsStatic:True;IsVirtual:False;IsGenericMethod:True;IsConstructor:False;IsFinal:False;"
         },
+        "System.String GetIndexMetrics[T](Microsoft.Azure.Cosmos.Response`1[T])[System.Runtime.CompilerServices.ExtensionAttribute()]": {
+          "Type": "Method",
+          "Attributes": [
+            "ExtensionAttribute"
+          ],
+          "MethodInfo": "System.String GetIndexMetrics[T](Microsoft.Azure.Cosmos.Response`1[T]);IsAbstract:False;IsStatic:True;IsVirtual:False;IsGenericMethod:True;IsConstructor:False;IsFinal:False;"
+        },
         "System.Threading.Tasks.Task`1[Microsoft.Azure.Cosmos.Response`1[System.Decimal]] AverageAsync(System.Linq.IQueryable`1[System.Decimal], System.Threading.CancellationToken)[System.Runtime.CompilerServices.ExtensionAttribute()]": {
           "Type": "Method",
           "Attributes": [