OK, this is inspired by Ben's
Foundry.
Name:
Coal MinerType: Action
Cost:
Reveal the top 3 cards of your deck, name a type and put the revealed cards of this type into your hand. Put any number of the other revealed cards onto your deck and discard the rest.
If you named ...
Action card,
+1 Action Treasure card, +
Victory card,
+1 Card per revealed Victory card,
+1 per revealed Victory card
Foundry's main problem is, as Fragasnap has pointed out, that it is a very strong BM card. My version rather suffers from the opposite problem, you might sometimes end up with "+2 Cards, +1$" if you choose
Treasures which is a bit worse than Smithy. But two coins is clearly too much.
As
Victory cards are often the worst choice I tried to add the VP token but it might not be enough.
With
Action cards this might be most (or even too) attractive, as it is a cantrip / Lab / Double Lab. You could also view it as a small Scrying Pool.
About the costs, my hunch is that it is too strong for 4 and too weak for 5, hence the debt cost. I am also not sure about whether the rest should be discarded or topdecked or both. Discarding seems cleaner and clearly better if you go for an engine. Topdecking might be better if you play a second Coal Miner.