Devil in the Details

You conjure a contract from thin air, stipulating the details of an arrangement with another creature. To you and any creatures who can read it, the contract's text appears normal, written in your hand, and conveys whatever meaning you intended when you conjured the text. At the end of the contract you may inlay an addendum, invisible for the duration or until the contract is signed. If the spell is dispelled, the invisible script appears. A creature with truesight can read the hidden message.