Supported features

dotjson uses JSON Schema to define the structure of the JSON objects to be returned by the model. dotjson supports most features from JSON Schema specification version 2020-12, and follows the specification unless otherwise specified.

For an introduction to JSON Schema, visit the official documentation.

Note

Compilation will fail if you pass a JSON Schema that contains keywords or combinations of keywords that are not supported. With an error message that specifies the unsupported construct.

Quick Reference

The following table is a quick reference for the keywords suported by dotjson. Keywords can interact in non-trivial ways and we strongly recommend you consult the usage guide.

Keyword / Area	Status	Notes
`type`	✅	`string`, `number`, `integer`, `boolean`, `null`, `array`, `object`.
`minLength` / `maxLength`	✅	Strings; counts characters.
`pattern`	✅	Most regex features; see unsupported regex list.
`format`	✅	Strictly enforced at generation time. Supports: `email`, `hostname`, `ipv4`, `uri`, `uri-reference`, `uuid`, `date`, `time`, `date-time`, `duration`.
`enum`	✅	Works for any type
`const`	✅	Works for any type.
`minimum` / `maximum`	✅	Numbers & integers.
`exclusiveMinimum` / `exclusiveMaximum`	✅	Numbers & integers.
`items`	✅	Homogeneous arrays. See note*
`prefixItems`	✅	Tuple validation (heterogeneous arrays).
`minItems` / `maxItems`	✅	Array length.
`required`	✅	Per object (including nested).
Optional fields	✅
`$defs` + `$ref`	✅	Internal refs only (no external refs).
Recursive schemas	✅	Unlimited depth supported.
`anyOf`	✅	Including at the root
`allOf`	✅
`additionalProperties`	✅️	Defaults to `false`.
`{}` or `{"type": "object"}`	✅️	Arbitrary JSON fields
`multipleOf`	✅	On integers
`oneOf`	✅	Treated as `anyOf`.
`propertyNames`	✅
`not`	❌	Not supported.
`if` / `then` / `else`	❌	Not supported
`dependentRequired`	❌	Not supported
`dependentSchemas`	❌	Not supported.
`patternProperties`	❌	Not supported.
`uniqueItems`	❌	Not supported.
`unevaluatedProperties` / `unevaluatedItems`	❌	Not supported.
Object size: `minProperties` / `maxProperties`	❌	Not supported.

Note: items can also be used for tuple validation along with additionalItems per the draft 2019-09 specification. However, we recommend using prefixItems for tuple validation and items for homogenous arrays or extra items beyond the prefixItems tuple.

Unsupported regular expressions

Certain regular expression patterns are not supported:

\b for word boundaries
Backwards references, e.g. \1 or (?P=open)
Conditional matches (?(1)a|b)
Lookbacks (?=bar)
Lookaheads foo(?=bar)
Lookbehinds (?<=foo)bar
Atomic groups (?>pattern)
Recursion (?R) or (?1)
Non-capturing groups (?:pattern)
Named captures (?P<name>pattern)
Inline modifiers (?i)case-insensitive
Subroutines \g<1>
Branch resets (?|pattern1|pattern2)
Inline comments (?#comment)
Code callouts (*MARK:name)
Version checks (*VERSION)
Whitespace-insensitive patterns, e.g. (?x)pattern # comment

Unsupported combinations

Certain keyword combinations are not supported and will cause compilation to fail.

Multiple string constraints (failing example)

Combining format with other string constraints like minLength/maxLength is not supported.

{
  "type": "object",
  "properties": {
    "email": {
      "type": "string",
      "format": "email",
      "minLength": 5
    }
  },
  "required": ["email"],
  "additionalProperties": false
}

Expected behavior: index compilation fails with an error indicating that combining format with other string constraints is unsupported. Remove the extra string constraints or validate them application‑side.

OpenAI Comparison