Part of the contract? The girl is agreeing to spend time with you and have sex with you. there are always going to be variations in different women.
If your first thought is that the girl has needle marks that just reveals your preconceptions rather than the reality
Yes part of the contract. Any transaction involves a contract.
In the absebce of any written terms, implied terms will apply.
So for example, most profiles state you pay for time only, sex is not being offered. Yet we all go for sex. Some prossies do make it clear sex is not on the cards, and punters that book those people will accept this. Some prossies will tell you from the outset their do's and dont's. Thats the contract. If the punter doesnt like it, they can go.
If keeping your clothes on (or a waist band or a butt plug or whatever) is important to you you must make it clear to the punter. No one will take offence at that, but not putting in and then expecting to insist on it will most likely annoy punters and will result in negative reviews because you are taking bookings under false pretences. If your do's or dont's are too much, you wont get many punters, but then if its important for you then you wont mind.