# MSG-066 — Opt-in confirmation must carry a working opt-out instruction

> The confirmation must include STOP instructions echoing a keyword the programme honours.

- **Rule ID:** MSG-066
- **Layer:** Message content (`MESSAGE_CONTENT`)
- **Checks:** `campaign.optin_message + campaign.optout_keywords`
- **Severity:** BLOCKING — Breaking this rule gets the submission rejected outright.
- **When it bites:** Gates approval — get this wrong and registration is refused
- **How it is detected:** AI judgement over the submitted form
- **Fix type:** Fix the field — a better value in the form clears it
- **Required by:** CTIA, FCC, TCR
- **Applies:** Applies to every 10DLC registration.
- **Canonical URL:** https://ekas.io/rules/10dlc/message-content/msg-066/

## Why this rule exists

A consumer who realises immediately that they did not mean to subscribe should be able to leave from the first message. The keyword named must be one the platform actually honours, or the instruction is worse than useless.

## How to fix it

Add "Reply STOP to cancel" and confirm STOP is in your declared opt-out keyword set.

## Example of a compliant value

```text
Reply HELP for help, STOP to cancel.
```