list-model.yml

swagger: '2.0'
info:
  version: '1.0'
  title: Example API
schemes:
  - http
paths:
  /lists:
    get:
      summary: Endpoint
      responses:
        200:
          description: Success
          schema:
            type: array
            items:
              $ref: '#/definitions/List'

definitions:
  List:
    description: List of items
    type: object
    properties:
      itemsCount:
        description: Number of items in the list
        type: number