I just laned as a WD with a Tide who spammed his nuke as soon as he had mana. Gave him my 2 clarities and he used them up, though I just wanted to give him 1.
It would have been an option to use the potion directly on him, but that's quite tricky when he's always in range of creeps and enemies.

So I suggest a general feature which allows you to request a certain item from the AI's current inventory by draging the desired item onto your hero.
This should be limited to consumables only.