Contract is missing some important query parameters:

Contract.type – so we can find specific contract types (e.g. consents)

Contract.subType – so we can find specific subTypes (e.g. opt-in consents)

Contract.applies – so that we can constrain the results to a timerange

Contract.action – so that we can constrain the results to specific actions (once action is better defined)

Contract.actor.entity – so that we can find contracts related to a specific actor
Contract.term.type, Contract.term.subType, Contract.term.subject, and Contract.term.actor.entity – for same reasons as above.

Contract.binding.bindingReference – so that when we have a known binding contract we can find the Contract instance(s) that uses it

Contract.friendly.contentReference – so that when we have a known friendly contract we can find the Contract instance(s) that use it.

Contract.legal.contentReference – so that when we have a known legal text (what ever that is) we can find the Contract instance(s) that use it.

Contract.rule.contentReference – so that when we have a known rules reference we can find the Contract instance(s) that use it.

Note on the contentReference – might be useful to just have a contentReference query that searches across all types.

Note might need a contentAttachment.url query too, as it is more likely that these are externally managed things that would be just URLs, not them also being FHIR resource types.