I too would like to see a schema for the XML types.
I found it recently.
You need to be authenticated to the API service in order to look at the file.
The base Yahoo Fantasy Sports API is defined here:
The base rng references other rngs such as Player, Game, League and so on.
I tried pasting the Player rng into a code block within this post but I wasn't able to. So instead, you can go here to see it.
in Fantasy Sports API