_create_tool_selection_response() — langchain Function Reference

Source Code

libs/langchain_v1/langchain/agents/middleware/tool_selection.py lines 47–78

def _create_tool_selection_response(tools: list[BaseTool]) -> TypeAdapter[Any]:
    """Create a structured output schema for tool selection.

    Args:
        tools: Available tools to include in the schema.

    Returns:
        `TypeAdapter` for a schema where each tool name is a `Literal` with its
            description.

    Raises:
        AssertionError: If `tools` is empty.
    """
    if not tools:
        msg = "Invalid usage: tools must be non-empty"
        raise AssertionError(msg)

    # Create a Union of Annotated Literal types for each tool name with description
    # For instance: Union[Annotated[Literal["tool1"], Field(description="...")], ...]
    literals = [
        Annotated[Literal[tool.name], Field(description=tool.description)] for tool in tools
    ]
    selected_tool_type = Union[tuple(literals)]  # type: ignore[valid-type]  # noqa: UP007

    description = "Tools to use. Place the most relevant tools first."

    class ToolSelectionResponse(TypedDict):
        """Use to select relevant tools."""

        tools: Annotated[list[selected_tool_type], Field(description=description)]  # type: ignore[valid-type]

    return TypeAdapter(ToolSelectionResponse)