{
  "type": "object",
  "properties": {
    "type": {"type": "string", "pattern": "^form-field$"},
    "id": {"type": "string", "pattern": "^[0-9a-f]{8}-([0-9a-f]{4}-){3}[0-9a-f]{12}$"},
    "machine_name": {"type": "string"},
    "data": {
      "type": "object",
      "properties": {
        "uid": {"type": "string","pattern": "^form-input-hidden$"},
        "title": {"type": "string"},
        "value": {"type": "string"}
      }
    }
  },
  "required": ["id", "type", "data"]
}

{
  "type": "form-field",
  "id": "c8a1af05-068f-4825-86d4-dd3c89943946",
  "machine_name": "hidden-input",
  "data": {
    "uid": "form-input-hidden",
    "title": "Hidden input",
    "value": "Default value"
  }
}