Function calling: GPT learns to speak JSON
In one sentence OpenAI adds 'function calling' to the API: the model returns structured JSON conforming to a schema, enabling reliable tool integrations without fragile prompt engineering.
Before June 13, 2023, if you wanted GPT to call an external API (say, check the weather or book a flight), you had to coax it into spitting out clean JSON via creative prompts. It worked 70% of the time, the rest was broken output.
OpenAI now makes this native: you describe the function (name, parameters, type) and the model returns JSON guaranteed to respect the schema. Reliability: ~99%.
It's the missing piece for building AI agents without fragility. From here on, every framework (LangChain, LlamaIndex, custom) integrates it as standard.
Companies
OpenAI
Tools
GPT-4, GPT-3.5-turbo
Tags
Sources