It shouldn't be "any number," because your opponent can just choose 0 each time. It should be they reveal their hand and discard either 1 or all cards with that CMC. Also, get rid of the "X is zero."

I think what dude1818 means is that "any number" should be "a number". "Any" infers that they have a choice, while "a number or cards" states that they have to do it.

I like the idea around Insanity, but, right now, it doesn't do anything, even if you changed 'any' to 'a'. I can just tell you that I can't do it. You see, it is mathematically impossible for me to discard a total of 3 casting cost worth of cards in my hand. It is impossible, therefore, I don't do it. I could be lying about that, too, but there isn't much you can do about it without calling in a third party or a judge.

What I think you want, and will work, would be:
Insanity (When this creature deals damage to an opponent, that player discards cards from their hand until they have discarded a combined converted mana cost worth of cards equal to or greater than ~'s power.

Which I admit, is messy. It's cool. I like it, but it's messy. It seems like the sort of concept you could make a rare around, or a mechanic that appears on a small number of creatures. There's no way in Pandemonium, though, that I would make that a keyword mechanic... unless I was designing Future Sight 2, and I was trying to send players for a loop.

Yeah, it is messy. If I could just make it cleaner and clearer...