Prescriptive

[Sarah]

Consisting in, or acquired by, immemorial or long-continued useand enjoyment; as, a prescriptive right of title; pleading thecontinuance and authority of long custom.The right to be drowsy in protracted toil has become prescriptive. J.M. Mason.

[Mark Zuckerberg]

saying exactly what must happen, especially by giving an instruction or making a rule:

[Monty]

Relating to the imposition or enforcement of a rule or method.