Function calling

Function calling is the mechanism that lets an AI model trigger your code instead of only producing text. You describe the functions available, look up an order, send an email, query the database, and the model decides when to call one, fills in the arguments, and uses the result to continue. It's the bridge between a chatbot that talks and an agent that acts.

For a founder this is what turns a language model into something useful in your business. Without it, the model can only describe what it would do; with it, the model actually does it, books the meeting, fetches the live number, updates the record. It matters because reliability now depends on your functions, not just the prompt. The model picks which function and what to pass, so good descriptions and validation on your side are what keep it from calling the wrong thing or passing junk arguments.