[.951 UI] Tribute offer is confusing
When an AI "offers tribute", he's actually demanding tribute. The trade window that shows the offer does not make it clear that you are agreeing to pay 10% of your income to him. There's a tooltip that lets you know that 10% of income is involved, but it's not clear whether you're paying him or he's paying you. In addition to that, unless you've gone into the diplomacy windows and seen the details of the demand tribute and offer tribute options, you have no idea of the term of the offer (30 seasons?) when this window pops up, so you have no idea of whether the offer is worthwhile or not.
