If one party's performance on a contract is substantial, the other party's duty to perform need only comport with the level of the rendered performance.

Comport

To conduct oneself or behave in a particular manner.

Substantial Performance

A legal concept indicating that a party has fulfilled enough of its contractual obligations to warrant payment, despite minor deviations from the initially agreed terms.

Rendered Performance

The act of providing or completing a service as per the terms of an agreement or contract.