How do you find out which wargoals your allies want?

I am trying to invite a potential ally into a war. On the invite attackers screen it says that they would be willing to join in exchange for a share of the spoils. However, I cannot figure out what they want in exchange for joining the war. Is there a way to find out?

Solution 1:

If they are your ally and you go to war, you set wargoals before actually declaring, so you can pause the game time and just play around with setting wargoals. Drag and drop any of the possibilities underneath the ally, making sure that it is they who are getting said spoil.

If you want more detail about what they would accept, check their war philosophy and neighbors/rivals. If they have neighboring rivals they will more likely want to war with them and take their planets (granted your military is better), and if their philosophy allows takeover then they would rather have the planets ceded to them. However if not, they may have a philosophy that only allows them to liberate planets. They won't accept if it's against their philosophy basically.