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Structured output schema builder

Turn one line field notation into a JSON Schema for structured model output and export request snippets for OpenAI strict mode, Anthropic and Gemini with restriction findings.

Write the fields, then press Build and check.

The restriction checks are a dated reading of each provider's documented limits, not a live probe, so a provider can accept more or less than this shows after a docs change. In OpenAI strict mode every field is required and optional ones gain null in their type, so treat null as absent in consuming code. Anthropic gets the schema through a tool's input_schema, and Gemini gets it as responseJsonSchema. Everything is built in this tab; nothing is uploaded and no provider is called.

Schema

Schema nameLetters, digits, hyphens, underscores, up to 64

Source

Field linesUp to 60,000 characters

One field per line. A trailing ? after the name makes it optional; one after the type makes it nullable. [] marks arrays, enum(a|b) lists values, braces add min, max, minLength, maxLength, minItems, maxItems, pattern. Indent two spaces to nest under an object or object[] line. Formats: date, date-time, time, email, uri, uuid.

Example output to validateOptional JSON the model might return

Ceilings: 300 fields, 8 nesting levels, 200,000 characters of example output. Patterns cannot contain spaces or a closing brace inside the braces notation.

Runs on this device. Nothing is uploaded.

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Structured output schema builder

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