cat.yaml

allOf:
  - $ref: 'pet.yaml'
type: object
properties:
  laziness:
    type: integer
    format: int64

catstore.yaml

swagger: '2.0'
info:
  version: '1.0.0'
  title: Swagger Catstore
schemes:
  - http
consumes:
  - application/json
produces:
  - application/json
paths:
  /pets:
    get:
      description: Returns all pets from the system that the user has access to
      responses:
        '200':
          description: pet response
          schema:
            type: array
            items:
              $ref: 'pet.yaml'
  /cats:
    get:
      description: Returns the cats in the system
      responses:
        '200':
          description: cat response
          schema:
            type: object
            title: Cats
            properties:
              cats:
                type: array
                items:
                  $ref: 'cat.yaml'

pet.yaml

type: object
required:
  - id
  - name
properties:
  id:
    type: integer
    format: int64
  name:
    type: string
  tag:
    type: string