Validation

Validation decorators

Each maps to the draft-07 keyword of the same meaning. They may target a property, a model, or a scalar declaration:

TypeSpec decorator	Schema keyword
@minLength / @maxLength	minLength / maxLength
@pattern	pattern
@format	format
@minValue / @maxValue	minimum / maximum
@minValueExclusive / @maxValueExclusive	exclusiveMinimum / exclusiveMaximum
@minItems / @maxItems	minItems / maxItems

model Product {
  @minLength(1) @maxLength(50) name: string;
  @minValue(0) @maxValueExclusive(1000000) price: float64;
  @minItems(1) @maxItems(10) tags: string[];
  @pattern("^[A-Z]{2}-\\d{4}$") sku: string;
  @format("uuid") id: string;
}

Product:
  type: object
  properties:
    name:
      type: string
      minLength: 1
      maxLength: 50
    price:
      type: number
      format: double
      minimum: 0
      exclusiveMaximum: 1000000
    tags:
      type: array
      items:
        type: string
      minItems: 1
      maxItems: 10
    sku:
      type: string
      pattern: ^[A-Z]{2}-\d{4}$
    id:
      type: string
      format: uuid
  required:
    - name
    - price
    - tags
    - sku
    - id

There is no uniqueItems output — @typespec/compiler has no decorator for it.

A bound whose value cannot be represented as a JSON number (e.g. @maxValue(9223372036854775807) on an int64), or that targets a date/time/duration value, is omitted with a warning instead of being emitted wrong — see unrepresentable-numeric-constraint and unsupported-temporal-range-constraint.