> For the complete documentation index, see [llms.txt](https://docs.esimpay.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.esimpay.net/eng/error-handling-1.md).

# Error Handling

### HTTP Status Codes

| Code  | Meaning          | Description          |
| ----- | ---------------- | -------------------- |
| `200` | OK               | Request successful   |
| `400` | Bad Request      | Invalid parameters   |
| `401` | Unauthorized     | Authentication error |
| `402` | Payment Required | Insufficient funds   |
| `409` | Conflict         | Conflict (duplicate) |
| `500` | Server Error     | Server-side error    |

### Error structure

```json
{
  "status": "ERROR",
  "message": "Error description"
}
```

***