Hmmm good question, perhaps out of realism, simplicity, fairness, and my diabolical sense to make things difficult, you won't need natures or abilities. I did say additional info is allowed, so things like personality is fine. In fact, it would make things interesting in that way. Like if a pokemon was backed into a corner it might use an ability like blaze. Or even being in the right area, like if a fire pokemon was in the volcanic region, it might have slightly better fire moves. But I do like freedom so I'll leave it up to you on how you'd like to RP your pokemon and such. Sorry about the confusion otherwise.
When making a post, there is the option on the far right that looks a little blue. It'll say spoiler when you put your mouse over it, or you can just use it manually and type out [SPOILER]