langchain/agents/load_tools.py/load_tools
def load_tools(
    tool_names: List[str],
    llm: Optional[BaseLanguageModel] = None,
    callbacks: Callbacks = None,
    **kwargs: Any,
) -> List[BaseTool]:
    """Load tools based on their name.

    Args:
        tool_names: name of tools to load.
        llm: Optional language model, may be needed to initialize certain tools.
        callbacks: Optional callback manager or list of callback handlers.
            If not provided, default global callback manager will be used.

    Returns:
        List of tools.
    """
    tools = []
    callbacks = _handle_callbacks(
        callback_manager=kwargs.get("callback_manager"), callbacks=callbacks
    )
    for name in tool_names:
        if name == "requests":
            warnings.warn(
                "tool name `requests` is deprecated - "
                "please use `requests_all` or specify the requests method"
            )

        if name == "requests_all":
            # expand requests into various methods
            requests_method_tools = [
                _tool for _tool in _BASE_TOOLS if _tool.startswith("requests_")
            ]
            tool_names.extend(requests_method_tools)
        elif name in _BASE_TOOLS:
            tools.append(_BASE_TOOLS[name]())
        elif name in _LLM_TOOLS:
            if llm is None:
                raise ValueError(f"Tool {name} requires an LLM to be provided")
            tool = _LLM_TOOLS[name](llm)
            tools.append(tool)
        elif name in _EXTRA_LLM_TOOLS:
            if llm is None:
                raise ValueError(f"Tool {name} requires an LLM to be provided")
            _get_llm_tool_func, extra_keys = _EXTRA_LLM_TOOLS[name]
            missing_keys = set(extra_keys).difference(kwargs)
            if missing_keys:
                raise ValueError(
                    f"Tool {name} requires some parameters that were not "
                    f"provided: {missing_keys}"
                )
            sub_kwargs = {k: kwargs[k] for k in extra_keys}
            tool = _get_llm_tool_func(llm=llm, **sub_kwargs)
            tools.append(tool)
        elif name in _EXTRA_OPTIONAL_TOOLS:
            _get_tool_func, extra_keys = _EXTRA_OPTIONAL_TOOLS[name]
            sub_kwargs = {k: kwargs[k] for k in extra_keys if k in kwargs}
            tool = _get_tool_func(**sub_kwargs)
            tools.append(tool)
        else:
            raise ValueError(f"Got unknown tool {name}")
    if callbacks is not None:
        for tool in tools:
            tool.callbacks = callbacks
    return tools