AI glossary · Agents and automation
Function calling
Function calling lets an AI model ask an app to run a specific action, like checking the weather or searching a database, and then use the result in its reply.
Also called tool use, tool calling, functions
In more detail
The model can’t browse or run code by itself. Instead, developers describe the tools available, and when one would help, the model replies with a structured request, such as “get_weather, city: Paris”. The app runs it and passes the result back.
This is what lets chatbots search the web, do accurate maths and work with your calendar. It is the core mechanism behind AI agents and the Model Context Protocol.
Example
You ask “Do I have anything on Friday?” and the assistant calls your calendar app, then summarises the events it gets back.
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