fixed failing test

Author: davemssavage

tests/server/fastmcp/test_tool_manager.py

@@ -40,7 +40,7 @@ class AddArguments(ArgModelBase):
             a: int
             b: int
 
-        fn_metadata = FuncMetadata(arg_model=AddArguments)
+        fn_metadata = FuncMetadata(arg_model=AddArguments, output_schema=None)
 
         original_tool = Tool(
             name="add",