Error Code Reference
| Code | Meaning | Fix |
|---|---|---|
| 401 | Unauthorized | Check your API key in Authorization header |
| 400 | Bad Request | Check required fields - to, message |
| 402 | Insufficient Credits | Top up your SMS credits |
| 422 | Invalid Phone Number | Use format 255XXXXXXXXX |
| 429 | Rate Limit Exceeded | Slow down requests - max 100/minute |
| 500 | Server Error | Try again or contact support |