Types

OMG has a rich type system that compiles to OpenAPI 3.1 schemas.

Primitive types

Type	Description	OpenAPI Mapping
string	Text	type: string
integer	Whole number	type: integer
number	Float/double	type: number
decimal	Precise decimal	type: number, format: decimal
boolean	True/false	type: boolean
date	Date only	type: string, format: date
datetime	Date and time	type: string, format: date-time
uuid	UUID string	type: string, format: uuid
any	Any type	{}

Objects

Define object schemas with typed fields:

{
  id: uuid,
  name: string,
  email: string,
  age: integer?    // Optional field
}

Nested objects

{
  user: {
    id: uuid,
    profile: {
      name: string,
      bio: string?
    }
  }
}

Arrays

Use [] suffix for arrays:

{
  tags: string[],           // Array of strings
  items: {                  // Array of objects
    id: uuid,
    name: string
  }[]
}

Enums

Define fixed value sets using union syntax:

{
  status: "draft" | "sent" | "paid",
  priority: "low" | "medium" | "high"
}

Union types

Combine types with |:

{
  value: string | integer,
  result: Success | Error
}

Optional fields

Mark fields as optional with ?:

{
  name: string,       // Required
  nickname: string?,  // Optional
  bio: string?        // Optional
}

Nullable fields

Allow null values with | null:

{
  deletedAt: datetime | null    // Required, can be null
}

Type references

Reference other defined types:

type Address {
  street: string,
  city: string,
  country: string
}

{
  id: uuid,
  name: string,
  address: Address    // Reference to Address type
}

Comments

Add descriptions with // comments:

{
  id: uuid,              // Unique identifier
  status: string,        // Current status
  amount: decimal        // Total amount in cents
}