Structured Outputs And Free Gemini Flash 20

OpenRouter's December 2024 update added structured outputs for OpenAI GPT-4o and Fireworks models. The feature lets an application specify the shape of a response through JSON Schema, so its code can expect particular fields and data types. Original announcement.

The documentation illustrates this with a weather response that requires a location as text and a temperature as a number. The application supplies that schema with its request instead of relying only on a prose instruction about formatting. The documentation says support is determined per endpoint, not just per model, so developers need a compatible provider endpoint for the constraint to apply. The announcement dates from 2024 and the documentation has since evolved, so current provider coverage should be checked there. Structured-output documentation.