Update app.py

app.py

@@ -105,7 +105,7 @@ class LangGraphAgent:
                 tool_fn = self.tools.get(tool_name)
                 if tool_fn:
                     try:
-                        tool_output = tool_fn(tool_input)
+                        tool_output = tool_fn.invoke(tool_input)
                         scratchpad = f"{raw_response}\nObservation: {tool_output}"
                         follow_up = self.model(content, scratchpad)
                         return {"messages": messages + [