Update app.py

app.py

@@ -276,6 +276,7 @@ class AnalyseAttachmentTool(Tool):
             "description": "Local path to the attachment file (e.g., 'documents/report.pdf').",
         }
     }
+    output_type = "string"
 
     def _run(self, file_path: str) -> str:
         """