AI 101

Function calling

Also known as: tool calling · tool use · function call

Inference

Function calling (tool calling) is when a model, instead of just replying with text, decides to call a function and provides the structured arguments for it.

The loop:

  1. You tell the model what functions exist.
  2. The model emits a call: get_weather(city="Bordeaux").
  3. Your code runs it, returns the result.
  4. The model uses the result to answer.

The leap from chat to action: function calling is how a model stops *describing* what to do and starts *doing* it. It's the foundation of every agent you'll ever build.