<!-- https://developers.silktide.com/v1/concepts/errors | Concepts -->

# Errors

A request that fails gets a `4xx` status when the request was wrong, or a `5xx` when Silktide could not answer. The body says what went wrong:

```json
{
  "error": {
    "type": "AccessDenied",
    "message": "Access denied",
    "properties": []
  }
}
```

| Field | What it is |
| --- | --- |
| `type` | What went wrong, such as `ModelNotFound`. It is stable, so branch on it. |
| `message` | A readable explanation, in the language of the key's user. It can change at any time, so show it, but never match on it. |
| `properties` | Details, when the error has any, as an object. An empty array (`[]`) when it has none. |

## Errors you will meet

| Status | Type | Means |
| --- | --- | --- |
| `400` | `InvalidRequest` | A parameter has a value Silktide does not accept, such as an id in the path that is not a whole number. `message` says what is wrong, and `properties.field`, when present, names the parameter. |
| `401` | `NotLoggedIn` | No key was sent, the key is wrong, or it belongs to another region. See [Authentication](https://developers.silktide.com/guides/authentication.md). |
| `403` | `AccessDenied` | The key cannot do this. The operation's page says what it needs under **Access**. |
| `404` | `ModelNotFound` | Nothing with that id exists in the account. |
| `429` | `TooManyRequests` | Too many requests. `properties.retryAfter` and the `Retry-After` header give the seconds to wait. See [Rate limits](https://developers.silktide.com/v1/concepts/rate-limits.md). |
| `503` | `ServiceUnavailable`, or another type | Silktide is busy. Retry after the number of seconds in `Retry-After`. |

Each operation's page lists the errors it can return, and what each means there.

## Results report some errors as `200`

The [results](https://developers.silktide.com/v1/concepts/results.md) operations, under `/v1/results/`, report errors they find while answering with status `200` and an `error` body in place of `result`. Check for `error` before you read `result`:

```javascript
const body = await response.json();
if (!response.ok || body.error) {
  throw new Error(body.error?.message ?? `HTTP ${response.status}`);
}
```

## Retrying

Retry `429` and `503` after the `Retry-After` header's seconds. Retry other `5xx` a few times with a growing wait. Do not retry other `4xx`: the same request will fail the same way.