How would I get a Player's Total RAP and Limiteds?

I'm making a place similar to Merely's Trade Hangout, but I don't know how to get a Player's RAP Value, and a list of all their Limiteds. I tried looking at MarketplaceService, and looking for some kind of roblox API, but couldn't find anything useful. I know it's possible, because other people have done it. Maybe I'm just bad at looking for things...

Thanks for any help. :)

I know I'm late but Merely's trade hangout and other games use usermade apis.

You could use something like this to get a list of a users inventory and rap value. http://roblox.plus:2052/inventory?username=call23re

That no longer works. Try this url instead: https://www.roblox.com/users/inventory/list-json?assetTypeId=8&itemsPerPage=30&pageNumber=1&thumbHeight=110&thumbWidth=110&userId=1337"