---
title: 1031: Idempotency-Key header is required on all sends; it makes blind retries safe | API Docs
description: Idempotency-Key header is required on all sends; it makes blind retries safe
---

Idempotency-Key header is required on all sends; it makes blind retries safe. This is an HTTP 400: the request could not be parsed.

## Troubleshooting

- Check this endpoint’s request schema in the API reference; `param` in the response names the exact field at fault.
- Use an official SDK, which enforces required fields and types before the call is made.

## Related

- [Sending a message](/channel/amb/api/resources/chats/subresources/messages/methods/send/index.md)