{
  "type": "object",
  "additionalProperties": false,
  "required": [
    "$sort",
    "by(x)"
  ],
  "properties": {
    "$sort": {
      "type": "array",
      "items": {
        "type": "integer",
        "minimum": 0
      }
    },
    "by(x)": {
      "type": "string"
    }
  }
}