Making sure player has 5 cards max in hand

Is there a way to monitor how many cards a player currently has in hand? The card game I’m attempting to make has a rule that says each player can only have 5 cards max. They can have less than 5 cards at any given time, but no more than 5.

A rule to limit it is fine, but it would be even better if a counter can be implemented so it displays how many cards a player currently has on the toolbar or in a public zone, so players can monitor each other.

Any ideas?