Keen Sense | Magic: The Gathering
Formats Keen Sense is Legal in
Official Oracle Text for Keen Sense
Whenever enchanted creature deals damage to an opponent, you may draw a card.
Official Rulings for Keen Sense
2/1/2007 : You draw one card each time the enchanted creature damages the opponent. This is not one card per point of damage.
2/1/2007 : If put on your opponent's creature, you do not draw a card when that creature damages you. The creature has to damage your opponent in order to have this work.
2/1/2007 : Drawing a card is optional. If you forget, you can't go back later and do it, even if it is something you normally do.