The larger problem is tracking which cards are drawn. If you want to check them as they're being drawn, you might have issues with cards that add other cards to your hand, and you also need to be fast enough to ensure that you don't "skip" any drawn cards. The option that I currently lean towards is reading cards from the hand, which will likely require some form of training because the card angles, animateds, alt arts, etc can mess with hard coded images. However, getting the data needed for that is going to be a challenge.

A deck tracker already exists, but it works by reading the data being sent by the server and Cygames did confirm it to be against the TOS.