{
  "type": "object",
  "properties": {
    "undelivered": {
      "type": "array",
      "items": { "type": "string", "example": "+1234567890" }
    },
    "resultCode": { "type": "integer", "example": 0 },
    "resultDescription": { "type": "string", "example": "SMS sent successfully" }
  }
}