SCHEMA SIGNAL NOTES
Method, sources & limits
This is a dated documentation review for Gemini Structured Outputs, checked on 24 October 2026 against the Google guide updated 21 October. It is independent and is not endorsed by Google.
What a finding means
The guide identifies eight ignored constraint families: string length, object property count, array uniqueness and array containment. Their snake_case spellings are also flagged. Other keywords outside this narrow profile are marked not assessed. A keyword can be inactive or appear in an unused definition; presence alone does not establish a practical failure.
We walk schema locations, including nested properties and definitions. Property names and example data are not mistaken for keywords. Inspection stops at 1,500 nodes or depth 40. References are not fetched, and reference behavior is not assessed.
Local validation is a different layer
Optional example JSON is checked with Ajv 8.20.0, using draft 2020-12 and strict keyword checking. Formats are not validated. Other schema dialects or unknown keywords may prevent compilation. A second local check removes only the documented ignored keywords. It illustrates a possible constraint gap; it does not reproduce a provider, SDK or model.
All built-in output examples were constructed for this site. They are not real model responses. No API request is made. Input is preserved, and the projected schema is never submitted as a suggested request.
Choose the right API entry
The current guide shows the Interactions API and response_format.schema. It is not the same request shape as generateContent configuration. Function parameters and parametersJsonSchema also have distinct rules. This tool accepts only a bare schema and generates no API request code.
What remains your responsibility
Model support, request limits, complex schemas, refusals, semantic correctness and intermediary transformations require separate checks. Keep application validation against your original schema. A clean report does not establish API acceptance or runtime success. Rule updates can lag provider changes.
Open-source credits
The local validator bundles Ajv and its dependencies. Retained license notices are included. Our interface and inspection logic were created with AI assistance.