# E12071 — SMSKeywordOperationUnknown

This keyword operation is not one Bird supports.

- **HTTP status**: `422`
- **Type**: `validation_error`
- **Name**: `SMSKeywordOperationUnknown`

## What to do

Use `stop`, `start`, `help`, or `custom`. Operations may be added over time, so read the current list from the keyword rules endpoint rather than hard-coding it.

## Related

- [E12xxx — SMS sending & delivery](/docs/api/errors/E12xxx): every code in this range
- [Errors](/docs/api/errors): the full wire contract, status mapping, and error catalog
- [Error handling](/docs/guides/errors): branching on `type` and `code`, validation details, and `vendor_code`