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You can use JSON Schema to define the structure of JSON objects returned by the model. We support most features from the JSON Schema 2020-12 specification across all of our products. We follow the specification unless otherwise noted.
The request will fail if you pass a JSON Schema that contains keywords or combinations of keywords that are not supported. The error message will specify the unsupported construct. Don’t hesitate to reach out to us to request support.

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Quick reference

KeywordStatusNotes
type✓string, number, integer, boolean, null, array, object
minLength / maxLength✓Strings; counts characters
pattern✓Most regex features; see unsupported patterns below
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 and integers
exclusiveMinimum / exclusiveMaximum✓Numbers and integers
multipleOf✓On integers
items✓Homogeneous arrays (see note below)
prefixItems✓Tuple validation (heterogeneous arrays)
minItems / maxItems✓Array length
required✓For object properties
Optional fields✓
$defs + $ref✓Internal refs only (no external refs)
Recursive schemas✓Unlimited depth
anyOf✓Including at the root
allOf✓
oneOf✓Treated as anyOf
additionalProperties✓Defaults to false
{}✓Arbitrary JSON
{"type": "object"}✓Arbitrary object fields
propertyNames✓
not✓
if / then / else✓
dependentRequired✓
patternProperties✓
minProperties / maxProperties✓
contains-Request support
mincontains / maxcontains-Request support
uniqueItems-Request support
dependentSchemas-Request support
unevaluatedProperties / unevaluatedItems-Request support
$dynamicRef-Request support
$dynamicAnchor-Request support
items can also be used for tuple validation along with additionalItems per the draft 2019-09 specification. We recommend using prefixItems for tuple validation and items for homogeneous arrays or extra items beyond the prefixItems tuple.

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Unsupported regular expressions

The pattern keyword supports most common regex features. The following are not supported:
  • Word boundaries (\b)
  • Backreferences (\1, (?P=open))
  • Conditional matches ((?(1)a|b))
  • Lookaheads (foo(?=bar))
  • Lookbehinds ((?<=foo)bar)
  • Atomic groups ((?>pattern))
  • Recursion ((?R), (?1))
  • 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 ((?x)pattern # comment)

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Next steps