Minimum permissions needed for SQL Compare?

I'm sure this has been asked (and answered) before, but I can't find anything in the forums. What is the minimum security/role needed to run SQL Compare against a prod DB? Surely there must be a way to perform a compare without using a sysadmin level login? We just tried a compare with a 'read only' login and most objects are missing on the prod side. We obviously don't want to assign individual permissions at the object level. Any suggestions appreciated!

UPDATE: I believe I just found a post on this. Sorry for the duplicate..