perf(core): invalidate cached tool_call_schema and args on field mutation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

libs/core/langchain_core/tools/base.py

@@ -555,6 +555,12 @@ class ChildTool(BaseTool):
         ignored_types=(functools.cached_property,),
     )
 
+    def __setattr__(self, name: str, value: Any) -> None:
+        super().__setattr__(name, value)
+        if name in {"args_schema", "description", "name"}:
+            self.__dict__.pop("tool_call_schema", None)
+            self.__dict__.pop("args", None)
+
     @property
     def is_single_input(self) -> bool:
         """Check if the tool accepts only a single input argument.

libs/core/tests/unit_tests/test_tools.py

@@ -3653,3 +3653,42 @@ def test_tool_default_factory_not_required() -> None:
     schema = convert_to_openai_tool(some_func)
     params = schema["function"]["parameters"]
     assert "names" not in params.get("required", [])
+
+
+def test_tool_call_schema_cache_invalidated_on_field_mutation() -> None:
+    """Verify cached tool_call_schema is invalidated when schema-affecting fields change."""
+
+    @tool
+    def my_tool(x: int) -> str:
+        """Original description."""
+        return str(x)
+
+    schema_before = my_tool.tool_call_schema
+    my_tool.description = "Updated description"
+    schema_after = my_tool.tool_call_schema
+
+    assert schema_before is not schema_after
+    assert schema_after.__doc__ == "Updated description"
+
+
+def test_args_cache_invalidated_on_args_schema_change() -> None:
+    """Verify cached args is invalidated when args_schema changes."""
+
+    class SchemaA(BaseModel):
+        x: int
+
+    class SchemaB(BaseModel):
+        y: str
+
+    @tool(args_schema=SchemaA)
+    def my_tool(x: int) -> str:
+        """A tool."""
+        return str(x)
+
+    args_before = my_tool.args
+    assert "x" in args_before
+
+    my_tool.args_schema = SchemaB
+    args_after = my_tool.args
+    assert "y" in args_after
+    assert "x" not in args_after