# invalid_idempotency_key

> `Idempotency-Key` must be 1–255 characters.

**Invalid Idempotency-Key** · HTTP 400

## What it means

`Idempotency-Key` must be 1–255 characters.

## What to do

Send a UUID.

## Example

```json
{
  "type": "https://api.bymundi.com/problems/invalid_idempotency_key",
  "title": "Invalid Idempotency-Key",
  "status": 400,
  "detail": "`Idempotency-Key` must be 1–255 characters.",
  "code": "invalid_idempotency_key",
  "requestId": "req_…"
}
```

How to read any error: [Errors guide](https://api.bymundi.com/docs/guides/errors.md).