Does an X in cost after an (X) mana need specification?

The first ability is completely fine as it, but does the second one even want to use the same X? If I understand correctly, that one is different, so I'd actually suggest rewording it slightly to avoid the confusion:

, Tap X creatures you control: Put X tax counters on target land.

Whenever an opponent taps a land for mana that has one or more tax counters on it, you may tap an untapped creature you control. If you do, you may draw up to one card for each tax counter on that land.