diff --git a/api/core/tools/tool_engine.py b/api/core/tools/tool_engine.py
index 997917f31c..3dce1ca293 100644
--- a/api/core/tools/tool_engine.py
+++ b/api/core/tools/tool_engine.py
@@ -246,7 +246,7 @@ class ToolEngine:
                     + "you do not need to create it, just tell the user to check it now."
                 )
             elif response.type == ToolInvokeMessage.MessageType.JSON:
-                result = json.dumps(
+                result += json.dumps(
                     cast(ToolInvokeMessage.JsonMessage, response.message).json_object, ensure_ascii=False
                 )
             else: