langchain/callbacks/manager.py/CallbackManagerForToolRun/on_tool_end
class CallbackManagerForToolRun:    def on_tool_end(
        self,
        output: str,
        **kwargs: Any,
    ) -> None:
        """Run when tool ends running."""
        _handle_event(
            self.handlers,
            "on_tool_end",
            "ignore_agent",
            output,
            run_id=self.run_id,
            parent_run_id=self.parent_run_id,
            **kwargs,
        )