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Definition

Function Calling

A capability of language models that allows them to generate structured function calls with typed parameters, enabling reliable interaction with external APIs and tools.

In Depth

Function calling is the mechanism that enables tool use. Instead of generating free-text that needs to be parsed, the model outputs structured JSON matching a predefined function schema. This makes interactions with external systems reliable and type-safe. Modern LLMs are trained specifically to generate accurate function calls, choosing the right function from a set of options and providing correct parameters based on the conversation context.

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