langchain/tools/base.py/BaseTool/run
class BaseTool:    def run(
        self,
        tool_input: Union[str, Dict],
        verbose: Optional[bool] = None,
        start_color: Optional[str] = "green",
        color: Optional[str] = "green",
        callbacks: Callbacks = None,
        **kwargs: Any,
    ) -> Any:
        """Run the tool."""
        parsed_input = self._parse_input(tool_input)
        if not self.verbose and verbose is not None:
            verbose_ = verbose
        else:
            verbose_ = self.verbose
        callback_manager = CallbackManager.configure(
            callbacks, self.callbacks, verbose=verbose_
        )
        # TODO: maybe also pass through run_manager is _run supports kwargs
        new_arg_supported = signature(self._run).parameters.get("run_manager")
        run_manager = callback_manager.on_tool_start(
            {"name": self.name, "description": self.description},
            tool_input if isinstance(tool_input, str) else str(tool_input),
            color=start_color,
            **kwargs,
        )
        try:
            tool_args, tool_kwargs = self._to_args_and_kwargs(parsed_input)
            observation = (
                self._run(*tool_args, run_manager=run_manager, **tool_kwargs)
                if new_arg_supported
                else self._run(*tool_args, **tool_kwargs)
            )
        except ToolException as e:
            if not self.handle_tool_error:
                run_manager.on_tool_error(e)
                raise e
            elif isinstance(self.handle_tool_error, bool):
                if e.args:
                    observation = e.args[0]
                else:
                    observation = "Tool execution error"
            elif isinstance(self.handle_tool_error, str):
                observation = self.handle_tool_error
            elif callable(self.handle_tool_error):
                observation = self.handle_tool_error(e)
            else:
                raise ValueError(
                    f"Got unexpected type of `handle_tool_error`. Expected bool, str "
                    f"or callable. Received: {self.handle_tool_error}"
                )
            run_manager.on_tool_end(
                str(observation), color="red", name=self.name, **kwargs
            )
            return observation
        except (Exception, KeyboardInterrupt) as e:
            run_manager.on_tool_error(e)
            raise e
        else:
            run_manager.on_tool_end(
                str(observation), color=color, name=self.name, **kwargs
            )
            return observation