Function Calling and Tool Use in LLMs

Function calling lets a language model recognise when a task requires an external action, like checking a database or sending an email, and generate a structured request for that action rather than trying to answer from its own knowledge.

This is the mechanism behind most modern AI agents, turning a text generator into something that can genuinely interact with business systems.

We spend significant design time on the function definitions themselves, since a poorly described tool leads the model to call it incorrectly or not at all.