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AI Agents · Function

function_tool

LangChain tools are callable functions that give agents access to data, code, databases, and actions. A chat model chooses when to call a tool and what arguments to pass.

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Syntax

@tool
def function_name(parameters) -> return_type:
    """Tool description."""
    ...

In-depth API docs are only for subscribers: parameters, examples, common mistakes and interview practice.

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  • Agents
  • Chat models
  • Tool calling
  • Tool integrations
  • LangSmith

Source: Tools. Checked 2026-11-03.