Validation constraints

apiary maps the common go-playground/validator rules you already write onto JSON-Schema constraints, with no extra annotations.

validate: rule	JSON Schema (by field type)
required	adds the field to required
min=N / max=N	minimum/maximum (number), minLength/maxLength (string), minItems/maxItems (array)
gt/gte/lt/lte=N	exclusiveMinimum/minimum/exclusiveMaximum/maximum (numbers)
len=N	exact length / item count
oneof=a b c	enum: [a, b, c]
email	format: email
uuid	format: uuid
url / uri	format: uri
ipv4 / ipv6	format: ipv4 / ipv6
hostname	format: hostname

Unknown rules are ignored. Constraints apply to request-body fields and to path/query/header parameters.

type CreateUserRequest struct {
    Username string `json:"username" validate:"required,min=3,max=32"`
    Email    string `json:"email"    validate:"required,email"`
    Role     string `json:"role"     validate:"oneof=admin user guest"`
    Age      *int   `json:"age,omitempty" validate:"gte=13,lte=120"` // nullable + bounded
}

generates:

username: { type: string, minLength: 3, maxLength: 32 }
email:    { type: string, format: email }
role:     { type: string, enum: [admin, user, guest] }
age:      { type: [integer, "null"], minimum: 13, maximum: 120 }
required: [username, email]

Go type to JSON Schema mapping

Go type	JSON Schema
string / bool	{type: string} / {type: boolean}
int, int32 / int64	{type: integer, format: int32 / int64}
float32 / float64	{type: number, format: float / double}
time.Time	{type: string, format: date-time}
uuid.UUID	{type: string, format: uuid}
[]T / map[K]V	array / object
Struct	$ref to a component
*T (scalar)	nullable (type: [T, "null"])
*Struct	nullable (anyOf: [{$ref}, {type: "null"}])

example: and default: tag values are coerced to the field's JSON type, so example:"42" on an integer field renders as example: 42, not "42".