{
  "responses": {
    "200": {
      "description": "Returns an array of pets",
      "type": "array",
      "items": {
        "$ref": "Pet"
      }
    },
    "400": {
      "description": "Invalid ID supplied",
      "type": "ErrorModel"
    },
    "404": {
      "description": "Pet not found"
    },
    "default": {
      "description": "Some other terrible error",
      "type": "ErrorModel"
    }
  }
}

{
  "responses": {
    "200": {
      "description": "Returns an array of pets",
      "type": "array",
      "items": {
        "$ref": "Pet"
      }
    },
    "400": {
      "description": "Invalid ID supplied",
      "$ref": "ErrorModel"
    },
    "404": {
      "description": "Pet not found"
    },
    "default": {
      "description": "Some other terrible error",
      "$ref": "ErrorModel"
    }
  }
}

Use "$ref" to point to models instead of "type"
Use "$ref" to point to models instead of "type"