This tool allows you to simulate playing cards. Click cards to indicate that you want to play them, then click the draw button to play those cards and draw new ones from your deck.
This tool is simple, and intended to be that way, it does not account for modifications to hand size or any other affects. It is merely a way for you to see what kind of hands you may draw while playing with this deck.
For anything more advanced than this it is best to play either in real life or on The Crucible Online.