Alternate wording that accomplishes the same thing, more wordily but without the confusing X:

As an additional cost to cast ~, you may sacrifice any number of artifacts. Search your library for an artifact card, and for an additional artifact card for each artifact sacrificed in this way. Reveal those cards and put them into your hand. Then shuffle your library.

I think the one I've got on the card is better, but comments welcome.

I prefer the one on the card. Or perhaps sacrifice any number of artifacts, then search your library for that many artifacts and one more...."?

(Do the rules require "up to" for library searching?)

The rules don't require it, but it's usually added for clarity. In any library search that's restricted (such as "artifact card" or "basic land card" rather than just "card"), you can always choose not to find what you're looking for.

That's what I thought, but I thought it was maybe easier to read without (since most players don't realise "up to" isn't automatic, although admittedly many players with good but not excellent rules knowledge may not get it) although on reflection, it may not be and you were right the first time.

Or "Sacrifice any number of artifacts. Search your library for at most one more artifact card and..." although I don't think that's any better either.

"As an additional cost to cast ~, you may sacrifice any number of artifacts. Search your library for up to X artifact cards, where X is 1 plus the number of artifacts sacrificed this way"?

That'd work, though that'd be even more wordy than the current wording...