As a GM in Dungeon World, when you introduce a magic item to the party, do you tell them the effects of the magic…

As a GM in Dungeon World, when you introduce a magic item to the party, do you tell them the effects of the magic…

As a GM in Dungeon World, when you introduce a magic item to the party, do you tell them the effects of the magic item, or do you wait for them to use it or have it identified?

I have a Bard in my party that came upon a glowing war horn but hasn’t thought to use it even once. I have the item’s description and its’ effects, but I haven’t thought of a good way to introduce it because I didn’t do it immediately.

How do you all handle this in your games?