langchain/callbacks/comet_ml_callback.py/CometCallbackHandler/on_tool_start
class CometCallbackHandler:    def on_tool_start(
        self, serialized: Dict[str, Any], input_str: str, **kwargs: Any
    ) -> None:
        """Run when tool starts running."""
        self.step += 1
        self.tool_starts += 1
        self.starts += 1

        resp = self._init_resp()
        resp.update({"action": "on_tool_start"})
        resp.update(flatten_dict(serialized))
        resp.update(self.get_custom_callback_meta())
        if self.stream_logs:
            self._log_stream(input_str, resp, self.step)

        resp.update({"input_str": input_str})
        self.action_records.append(resp)