diff --git a/openapi/openapiv2.json b/openapi/openapiv2.json
index b99727843..02a028e6d 100644
--- a/openapi/openapiv2.json
+++ b/openapi/openapiv2.json
@@ -13471,6 +13471,16 @@
         "startDelay": {
           "type": "string",
           "description": "Time to wait before dispatching the first activity task. This delay is not applied to retry attempts."
+        },
+        "requestedStartTime": {
+          "type": "string",
+          "format": "date-time",
+          "description": "The time at which the activity is requested to start, computed as `schedule_time + start_delay`.\nSame as `schedule_time` if `start_delay` is not set."
+        },
+        "actualStartTime": {
+          "type": "string",
+          "format": "date-time",
+          "description": "The time at which the activity was first dispatched to a worker (i.e. when a worker first picked\nup the task from matching). Not set until a worker picks up the first attempt. Not updated on\nsubsequent retry attempts."
         }
       },
       "description": "Information about a standalone activity."
diff --git a/openapi/openapiv3.yaml b/openapi/openapiv3.yaml
index a0288e082..764e46d73 100644
--- a/openapi/openapiv3.yaml
+++ b/openapi/openapiv3.yaml
@@ -9852,6 +9852,19 @@ components:
           pattern: ^-?(?:0|[1-9][0-9]{0,11})(?:\.[0-9]{1,9})?s$
           type: string
           description: Time to wait before dispatching the first activity task. This delay is not applied to retry attempts.
+        requestedStartTime:
+          type: string
+          description: |-
+            The time at which the activity is requested to start, computed as `schedule_time + start_delay`.
+             Same as `schedule_time` if `start_delay` is not set.
+          format: date-time
+        actualStartTime:
+          type: string
+          description: |-
+            The time at which the activity was first dispatched to a worker (i.e. when a worker first picked
+             up the task from matching). Not set until a worker picks up the first attempt. Not updated on
+             subsequent retry attempts.
+          format: date-time
       description: Information about a standalone activity.
     ActivityExecutionListInfo:
       type: object
diff --git a/temporal/api/activity/v1/message.proto b/temporal/api/activity/v1/message.proto
index 6d77c7f12..55d6eca17 100644
--- a/temporal/api/activity/v1/message.proto
+++ b/temporal/api/activity/v1/message.proto
@@ -186,6 +186,15 @@ message ActivityExecutionInfo {
 
     // Time to wait before dispatching the first activity task. This delay is not applied to retry attempts.
     google.protobuf.Duration start_delay = 37;
+
+    // The time at which the activity is requested to start, computed as `schedule_time + start_delay`.
+    // Same as `schedule_time` if `start_delay` is not set.
+    google.protobuf.Timestamp requested_start_time = 38;
+
+    // The time at which the activity was first dispatched to a worker (i.e. when a worker first picked
+    // up the task from matching). Not set until a worker picks up the first attempt. Not updated on
+    // subsequent retry attempts.
+    google.protobuf.Timestamp actual_start_time = 39;
 }
 
 // Limited activity information returned in the list response.