diff --git a/src/gradient_labs/_conversation_return_async_tool_result.py b/src/gradient_labs/_conversation_return_async_tool_result.py
new file mode 100644
index 0000000..3d7e9d1
--- /dev/null
+++ b/src/gradient_labs/_conversation_return_async_tool_result.py
@@ -0,0 +1,66 @@
+from typing import Optional, Any, Dict
+from datetime import datetime
+
+from dataclasses import dataclass
+from dataclasses_json import dataclass_json
+
+from ._http_client import HttpClient
+
+
+@dataclass_json
+@dataclass(frozen=True)
+class ReturnAsyncToolResultParams:
+    """Parameters for returning an async tool execution result.
+
+    When a tool is configured for asynchronous execution, the agent will request
+    the tool execution via an action.execute webhook event, and your system should
+    return the result using this method.
+    """
+
+    # async_tool_execution_id is the unique identifier for the async tool execution.
+    # This ID is provided in the action.execute webhook event when the agent
+    # requests the tool execution.
+    async_tool_execution_id: str
+
+    # payload is the result data from the tool execution as a JSON object.
+    # The structure of this object depends on your tool's implementation.
+    # The agent will use AI to extract relevant information from any well-formed
+    # JSON object.
+    payload: Dict[str, Any]
+
+    # timestamp optionally defines the time when the result was generated.
+    # If not given, this will default to the current time.
+    timestamp: Optional[datetime] = None
+
+
+def return_async_tool_result(
+    *, client: HttpClient, conversation_id: str, params: ReturnAsyncToolResultParams
+) -> None:
+    """Returns the result of an async tool execution.
+
+    When a tool is configured for asynchronous execution, the agent will request
+    the tool execution via an action.execute webhook event, and your system should
+    return the result by calling this function.
+
+    This allows your system to perform long-running operations without blocking the
+    conversation, and return results when they're ready.
+
+    Important Notes:
+    - The conversation must be in an ongoing state. You cannot return async tool
+      results to conversations that are finished, failed, or cancelled.
+    - Make sure to use the correct async_tool_execution_id from the action.execute
+      webhook event.
+    - The result payload should be a valid JSON object containing the data the
+      agent needs to continue the conversation.
+    """
+    body = {
+        "async_tool_execution_id": params.async_tool_execution_id,
+        "payload": params.payload,
+    }
+    if params.timestamp:
+        body["timestamp"] = client.localize(params.timestamp)
+
+    _ = client.put(
+        f"conversations/{conversation_id}/return-async-tool-result",
+        body=body,
+    )
diff --git a/src/gradient_labs/client.py b/src/gradient_labs/client.py
index 7360811..ff17833 100644
--- a/src/gradient_labs/client.py
+++ b/src/gradient_labs/client.py
@@ -15,6 +15,10 @@
 from ._conversation_resume import resume_conversation, ResumeParams
 from ._conversation_read import read_conversation, ReadParams
 from ._conversation_start import start_conversation, StartConversationParams
+from ._conversation_return_async_tool_result import (
+    return_async_tool_result,
+    ReturnAsyncToolResultParams,
+)
 
 from ._handoff_target_upsert import upsert_hand_off_target, UpsertHandOffTargetParams
 from ._handoff_targets import list_handoff_targets, HandOffTargets
@@ -208,6 +212,26 @@ def add_message(
             params=params,
         )
 
+    def return_async_tool_result(
+        self,
+        *,
+        conversation_id: str,
+        params: ReturnAsyncToolResultParams,
+    ) -> None:
+        """Returns the result of an async tool execution.
+
+        When a tool is configured for asynchronous execution, the agent will request
+        the tool execution via an action.execute webhook event, and your system should
+        return the result by calling this method.
+
+        This allows your system to perform long-running operations without blocking the
+        conversation, and return results when they're ready."""
+        return_async_tool_result(
+            client=self.http_client,
+            conversation_id=conversation_id,
+            params=params,
+        )
+
     def upsert_hand_off_target(self, *, params: UpsertHandOffTargetParams) -> None:
         """upsert_hand_off_target inserts or updates a hand-off target.