The Sentinel feat grants a number of benefits (PHB, p. 169-170):
- When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn.
- Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.
- When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.
If a character has the Sentinel feat, would enemies know, so that they avoid attacking someone else or disengaging? Or when/how would they find out if they don't know to begin with?
As far as I can see there is no "official" answer so I am looking for the community's consensus. If you can point me to a rules as written answer that would be great.
My thoughts are that an enemy would not know unless they also had the Sentinel feat (or other martial prowess?). One without the feat would figure it out after being attacked (or maybe hit?) by a use of the feat.