Expected:
Given an an IT Service Management JSM project and a couple of services (Operations) in the project, when API clients make a call to:

/rest/servicedeskapi/servicedesk/{serviceDeskId}/requesttype/{requestTypeId}/field

then the client should have enough information to construct a valid service request.

Actual:
Currently, the API returns

...
"validValues": []
...

When customers set Affected Services as a mandotory field, this prevents clients from being able to construct a valid service request.

Suggested solution:
The result can be more hypermedia oriented with an href element to a secondary endpoint that is the authority on assets. Of course, clients must expect to use the URL as a search, rather than a complete enumeration.