init() — langchain Function Reference

Architecture documentation for the __init__() function in tool_selection.py from the langchain codebase.

Function python LangChainCore MessageInterface

Entity Profile

LangChainCore→ MessageInterface→ __init__() — langchain Function Reference

Dependency Diagram

graph TD
  74e81f5f_ce46_4e5d_763f_ed260d0dbec3["__init__()"]
  888c953d_8f6f_ac7f_4274_ca04589e186a["LLMToolSelectorMiddleware"]
  74e81f5f_ce46_4e5d_763f_ed260d0dbec3 -->|defined in| 888c953d_8f6f_ac7f_4274_ca04589e186a
  style 74e81f5f_ce46_4e5d_763f_ed260d0dbec3 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/langchain_v1/langchain/agents/middleware/tool_selection.py lines 122–156

    def __init__(
        self,
        *,
        model: str | BaseChatModel | None = None,
        system_prompt: str = DEFAULT_SYSTEM_PROMPT,
        max_tools: int | None = None,
        always_include: list[str] | None = None,
    ) -> None:
        """Initialize the tool selector.

        Args:
            model: Model to use for selection.

                If not provided, uses the agent's main model.

                Can be a model identifier string or `BaseChatModel` instance.
            system_prompt: Instructions for the selection model.
            max_tools: Maximum number of tools to select.

                If the model selects more, only the first `max_tools` will be used.

                If not specified, there is no limit.
            always_include: Tool names to always include regardless of selection.

                These do not count against the `max_tools` limit.
        """
        super().__init__()
        self.system_prompt = system_prompt
        self.max_tools = max_tools
        self.always_include = always_include or []

        if isinstance(model, (BaseChatModel, type(None))):
            self.model: BaseChatModel | None = model
        else:
            self.model = init_chat_model(model)