Errors

{
  "error": {
    "code": "validation_failed",
    "message": "The email field must be a valid email address.",
    "fields": {
      "email": ["The email field must be a valid email address."]
    }
  }
}

const res = await fetch(url, options);
if (!res.ok) {
  const { error } = await res.json();
  switch (error.code) {
    case 'whatsapp_window_closed':
      return sendTemplateInstead();
    case 'plan_limit_reached':
      return notifyBilling(error.details);
    case 'rate_limited':
      return retryAfter(res.headers.get('Retry-After'));
    default:
      // A code this build predates: fall back to the HTTP status.
      return res.status >= 500 ? scheduleRetry() : failPermanently(error);
  }
}