"The operation is initiated by a named query, using _query=generate on the /DocumentReference end-point:

GET [service-url]/DocumentReference/?_query=generate&uri=:url&...

The "uri" parameter is a relative or absolute reference to one of the document types described above. Other parameters may be supplied:"

GET is only allowed for operations that don't affect state. Generating a new resource obviously impacts state, so this should be performed using POST only. As well, it should be formally defined as an operation rather than using the old "named query" label.