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AI & Machine Learning · Foundational

Function Calling

An API feature where a model outputs a structured request to call a developer-defined function with arguments.

Definition

Function calling (the term used by OpenAI, Azure and Google; Anthropic calls it tool use) turns natural-language requests into JSON arguments for code. It is used for retrieving data, taking actions and producing structured output.

Example

User asks for the weather; the model returns get_weather({"city": "Austin"}).

Exam tip

Function calling and tool use are the same concept under different vendor names.

Related terms