Structured Outputs

OpenAI · 6 August 2024

Structured Outputs guarantee model responses conform to a developer-supplied JSON Schema, launched with gpt-4o-2024-08-06.

Uses constrained decoding with precomputed grammar indexes so output cannot violate the schema, ending invalid-JSON failures that function calling still had. Core plumbing for reliable tool use.

Date: Tuesday, 6 August 2024
Lab: OpenAI
Kind: feature
Access: closed API

Constrained-decoding mechanism is as described by Simon Willison's DevDay 2024 notes.

Sources

developers.openai.com/api/docs/changelog
simonwillison.net/2024/Oct/1/openai-devday-2024-live-blog/

This record was checked against its sources on 6 October 2026. How we check

Function calling in Chat Completions

Structured Outputs

Sources

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