# reason_required

> Every trade needs a reason (X-Reason).

Source: https://tickwire.io/docs/errors/reason_required/

HTTP 400. Nothing reached the broker.

**Likely causes:**

- The X-Reason header is missing.
- An MCP trading tool was called without a `reason`.

**What to do:** Say why in X-Reason (or the MCP tool's `reason`).

**Retry:** No. The same request gets the same answer; change something first.

Listed under [Orders and idempotency](https://tickwire.io/docs/errors/#orders-and-idempotency) in [Errors](https://tickwire.io/docs/errors/). Send the error's `requestId` to support and we can find the request.