# Error: invalid_idempotency_key

> The Idempotency-Key header is malformed

Source: https://docs.vlayers.ai/errors/invalid_idempotency_key

- HTTP status: 400
- Retry: No: fix the request first

## What happened

The Idempotency-Key header is malformed.

## Why

An `Idempotency-Key` header was sent but is empty, longer than 255 characters, or holds characters outside printable ASCII.

## How to fix it

Send 1–255 printable ASCII characters (a UUID works), or leave the header out.

## Example response

```json
{
  "error": "invalid_idempotency_key",
  "message": "The Idempotency-Key header is malformed.",
  "requestId": "req-8f2c1d4b",
  "retryable": false,
  "docs": "https://docs.vlayers.ai/errors/invalid_idempotency_key"
}
```