In general, people may provide cards if they have them.
However, I will usually just be using the dragon's visual traits and how (if at all) they translate into wyrmside to determine genetics.
Example: Cresting on various forms of fire dragons, will be treated as Crest: xX though it doesn't appear on cards. Starburst will become Lace. etc.
So it will be purely on visual if you don't have a card. If there's something hidden... well, sorry. I can't do anything about that, and most of the hidden traits were genetic diseases and other things that we won't incorporate.