I presume your new to MLS? It's a secret, it's a really stupid rule so don't bother looking into it too much. The gist of it is:I did a Google search and struck out. Is there a web page we can go to and see the Discovery List?
Teams can place 10 players on their "discovery list" think of it like calling dibs
If someone else tries to sign a player you called dibs on, you get the first chance to offer them a deal, if the other team wants to make a bigger offer they have to pay you for your dibs.
Teams don't want to tell who's on their discovery list to prevent bidding wars.