Status Codes

{
  "success": false,
  "statusCode": 423,
  "message": "Service inactive",
  "data": {
    "hint": "Your subscription has expired. Please check your dashboard or contact support."
  }
}

const body = await res.json();

switch (body.statusCode) {
  case 401:
    throw new Error("API key is invalid or disabled");
  case 403:
    throw new Error("This key's role cannot do that");
  case 429:
    return retryWithBackoff();      // the only common transient one
  case 423:
  case 426:
    throw new Error("Billing needs attention — pausing");   // never retry
  default:
    throw new Error(`${body.statusCode}: ${body.message}`);
}