Okay, how about this then:
When you drink water purified with tablets bought from Petrarch, roll +weird. On 10+, the water's fine. On a 7-9, either you or someone else drink contaminated water.
Well, the move shouldn't determine if the water is fine. You, as the MC, should using your principles, prep and agenda, right? Then, depending on whether the PC uses a "good" purification tablet or not we can discern whether there is an effect or not.
I think I know what you're trying to get at with this, but I think you're wording these moves in a way that doesn't reflect what's actually happening in the fiction.
So, in the example above, you might say, "On a 10+, you can discern whether the water is purified or not" instead of "the water's fine".
See the difference? In one case, the water is either fine or not and the player is gathering information about it. In the latter (your original), the move is determining the fiction based on... what? Nothing really.
So, your moves need to be grounded in, and attached to the fiction and the PC's actions in the game.
As far as when to reveal the details of the specific move, I think that's up to each individual MC and each individual move. Sometimes you may want to just throw it right out there (and I think that'd fall under "tell possible consequences and ask"). "If you drink it, you'll need to make this move... *showing them the move* You sure you want to do that?"
Or, maybe not. Maybe you just announce future badness. "When you lean in to cup the water in your hands, there's a strange odor. Do you drink it anyways? Great. Roll+sharp for me." And, then just tell them the effects of what they scored.
For some moves, like if they are using Sharp to detect something they shouldn't know, keeping the move hidden may be best.