D&D 5E (2014) How do you DM Mage Hand Legerdemain and oil/acid/holy water

[Vaalingrade]

I would argue flatly that if there is a chance of causing any damage (hp loss) then it’s an attack.
Pouring oil per se could not cause damage so I can’t see it as an attack. Holy water on a vampire would be an attack as it would cause hp loss if successful.

What about pouring holy water on just a normal dude, or normal water on a vampire.

Kind of weird that magic knows how you're tipping out that vial and works expressly to hose the player.