This paper suggests a reason, other than asymmetric formation, why agency contracts are not explicitly contingent on the contracting parties' performances or actions. This reason is the formal nature of contracts: the form, usually written, that contracts are required to take to be enforceable in a court of law by legal prescription, common practice or simply by the contracting parties' will. We model the formal nature of contracts as the requirement that the mapping from the domain of the contract into the corresponding remunerations must be of an algorithmic nature. We show that there exist situations in which the chosen contract cannot be explicitly contingent on the parties' performance although, in principle, such performances are cont...