I think that not making this "you may play it" is a big mistake. Sure, it removes an (extremely small) amount of "complexity", but in return you'll get a lot of resentment when people are forced to play Remake, Trading Post, Junk Dealer etc. and trash a good card from their hand. It's not as bad as the possibility of being forced to trash a good card with Lookout, but it's the kind of luck based risk that isn't fun and isn't present in many other dominion cards.
Also it makes the same mistake as Wishing Well (and Ironmonger, although that card's not as annoying because it always gives you SOME benefit) by not having the ability to combo with top decking cards. It definitely comes across as more annoying than a deliberate design choice. It won't be annoying as Wishing well, where you're forced to make a random guess even though you've invested in cards that allow more predictability, but it probably would have been better served by having the effects reversed, or having a vanilla effect that doesn't have +cards (similar to how Mystic "fixed wishing well). Instead it's a spammable cantrip that is occasionally excellent, with the only strategic element being "buy it if you have a lot of actions".
The overpay effect is cool, and seems to be the real purpose of the card, but it seems like an accident that it doesn't actually help the card its attached to. A stash-like "anywhere in your deck" effect would have fixed that.
This card will be good, but it reminds me of a fan-card. I wouldn't put it alongside failed cards like Thief, Scout or Counting House, but it does seem haphazardly designed.