The job that a contract has to do ought to be simple, even when the suppliers have to manage lots of complexity to deliver the services.
A contract will say what responsibilities the supplier takes on, and what they will be paid for doing so. Of course there are caveats and exclusions, and assumptions, and customer provided elements, and all the usual paraphernalia of a contract, but ultimately it comes down to the question: What is one party obliged to do for the other?
The problem is writing down exactly what you want and exactly what is supposed to happen when things go wrong. We’ve talked before about contracting with suppliers to sign up to outcomes, not inputs ( here ), and last time whilst addressing target setting and performance management we said that there was a real danger that the targets used to drive behaviour could backfire, sometimes spectacularly. People chase targets, in particular if they are likely to suffer financially from not hitting them.