It would be nice if when you send a CF it can come with a "notes" box whereby a kingdom can enter Terms and conditions and when it gets broken you can hover over it to see what them terms were... Could also appear in your relations page and it will say what the "notes" were so there is a track record. That would be official then and no bs agreements on IRC or PMs and the whole kingdom can see them.
People should still be able to break but then again there is a clear viewing to all what the terms were originally.
To be fair in the old days CF would be written down and handed to people as a record.