diff --git a/langchain_glm/callbacks/agent_callback_handler.py b/langchain_glm/callbacks/agent_callback_handler.py
index df5c1b3..64482e8 100644
--- a/langchain_glm/callbacks/agent_callback_handler.py
+++ b/langchain_glm/callbacks/agent_callback_handler.py
@@ -131,7 +131,7 @@ async def on_tool_start(
 
     async def on_tool_end(
         self,
-        output: str,
+        output: Any,
         *,
         run_id: UUID,
         parent_run_id: Optional[UUID] = None,
@@ -143,7 +143,7 @@ async def on_tool_end(
             "run_id": str(run_id),
             "status": AgentStatus.tool_end,
             "tool": kwargs["name"],
-            "tool_output": output,
+            "tool_output": str(output),
         }
         self.queue.put_nowait(dumps(data))