# idempotency_key_missing (HTTP 400)

idempotency_key_missing (HTTP 400) from the GetItDone API: An Idempotency-Key was required for this call but none was supplied or it was malformed.

- **HTTP status:** 400
- **Problem type URI:** https://nowgetitdone.com/docs/api/problems/idempotency-key-missing

## What it means

An Idempotency-Key was required for this call but none was supplied or it was malformed.

## Likely causes

- The header was omitted where the client library expected one.
- The header value was empty or longer than 255 characters.

## How to fix

- Send an `Idempotency-Key` header (1–255 visible ASCII characters; a UUID works well).
- Reuse the SAME key when retrying the SAME request to replay the first result.

## Example problem+json

```json
{
    "type": "https://nowgetitdone.com/docs/api/problems/idempotency-key-missing",
    "title": "Idempotency-Key header required",
    "status": 400,
    "code": "idempotency_key_missing",
    "request_id": "req_a1b2c3d4"
}
```

## Related

- [Idempotency](/docs/api#idempotency)