OpenAiStructuredOutput

Converts a Schema.Codec to OpenAI structured-output JSON Schema and a matching codec for model output.

When to use

Use when you send Effect Schema-backed structured output requests to OpenAI standard models and need provider-compatible JSON Schema without losing the decoded application type.

Details

Returns the JSON Schema to include in the request and the codec to use when decoding the model response. The codec remains authoritative: the provider JSON Schema can be a lossy, less restrictive representation when OpenAI cannot express an Effect Schema constraint. Conversion throws when the resulting root is not an object or contains anyOf.

Gotchas

• Some schemas use a provider-safe encoded shape: tuples become objects with numeric string keys, objects with index signatures become arrays of [key, value] pairs, and optional properties become required nullable properties.
• oneOf unions are emitted as anyOf unions.
• Compatible regex patterns are merged because OpenAI structured output does not support allOf.
• The root JSON Schema must be an object and cannot use anyOf.
• Constraints inside allOf are retained only when they have an explicit, semantics-preserving normalization rule.
• Structural constraints inside allOf, such as properties, required, additionalProperties, and items, are omitted instead of being merged with a different meaning.
• Unsupported constraints are removed from the provider schema and are still checked while decoding with the returned codec.
• Compatibility targets standard OpenAI models. Fine-tuned models support a smaller JSON Schema subset.

declare function toCodecOpenAI<T, E, RD, RE>(schema: ConstraintCodec<T, E, RD, RE>): {
  codec: ConstraintCodec<T, unknown, RD, RE>;
  jsonSchema: JsonSchema;
}