Engagement bait
Why it matters for creators
This matters for comment-to-DM specifically, because "comment a keyword and I'll send you the link" can look like engagement bait at a glance and is not.
The distinction Meta's policies draw is whether the interaction is the point or the mechanism. "Tag three friends to enter" asks for interaction as an end in itself — the tags do nothing for the person tagging. "Comment GUIDE and I'll send it over" uses a comment as the route to something the person actually wants, and they get it. One is a toll, the other is a doorbell.
Staying on the right side is mostly about what happens next. If the comment reliably produces the promised thing, quickly, the mechanic is honest and the engagement is real. Where it tips over is asking for tags or shares as a condition, adding steps that serve you rather than them, or promising something that never arrives — which is also the fastest way to train an audience to ignore your keywords.