Function calling is an API feature OpenAI released in June 2023, soon adopted with their own twists by Anthropic, Google and others. The developer supplies a list of functions described as JSON schemas; the model decides which one to invoke and with what arguments, then returns a structured JSON payload. It is essentially Tool Use standardised at the API level instead of relying on raw prompt engineering — and the guarantee that the output is valid JSON is a serious engineering win. Nearly every modern AI Agent is built on top of this capability; the design of the Tool Definition Schema often determines whether the product works at all.
MEVZU N°124ISTANBULYEAR I — VOL. III
Glossary · Intermediate · 2023
Function Calling
An API feature that lets a model invoke a predefined function via structured JSON output.
- EN — English term
- Function Calling
- TR — Turkish term
- Fonksiyon Çağırma