diff --git a/backend/open_webui/utils/middleware.py b/backend/open_webui/utils/middleware.py
index 8b17d7058..79d115351 100644
--- a/backend/open_webui/utils/middleware.py
+++ b/backend/open_webui/utils/middleware.py
@@ -1857,6 +1857,9 @@ async def process_chat_response(
                             except Exception as e:
                                 tool_result = str(e)
 
+                        if isinstance(tool_result, dict):
+                            tool_result = json.dumps(tool_result)
+
                         results.append(
                             {
                                 "tool_call_id": tool_call_id,