> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sendykit.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Errors

> SendyKit API error format and common error codes

## Error envelope

SendyKit error responses use this shape:

```json theme={null}
{
  "error": "subscriber not found",
  "code": "not_found"
}
```

## Common error codes

| Code              | Meaning                        |
| ----------------- | ------------------------------ |
| `unauthorized`    | Missing or invalid auth        |
| `forbidden`       | Authenticated, but not allowed |
| `not_found`       | Resource does not exist        |
| `invalid_request` | Missing or invalid input       |
| `internal_error`  | Unexpected server-side failure |

## Common statuses

| Status | Typical cause                               |
| ------ | ------------------------------------------- |
| `400`  | Invalid request body, query, or params      |
| `401`  | Missing or invalid API key / token          |
| `402`  | Machine payment required for premium action |
| `403`  | Auth ok, permission denied                  |
| `404`  | Resource not found                          |
| `409`  | Idempotency or state conflict               |
| `500`  | Internal server error                       |

## Source of truth

Defined in:

* `internal/respond/respond.go`
* `docs/AUTH-BILLING-MATRIX.md`