Earlier today, somebody was asking why his search http://beta.musicbrainz.org/ws/2/artist/?fmt=json&query=artist%3AOlyam&type=artist&limit=25 did fail with an error message of

"type is not a valid parameter unless releases or release-groups are requested."

http://beta.musicbrainz.org/doc/Development/XML_Web_Service/Version_2/Search documents the type parameter as common to all resources and meaning:

Selects the index to be searched, artist, release, release-group, recording, work, label (track is supported but maps to recording)

but if you use it on anything other than release or release-group searches, you get the error message above. Additionally, if you use it on release or release-group searches, the only valid values for it are release group types, not index names as the documentation suggests. So unless I misunderstood something, the type parameter is only a shortcut for the type field on release and release group searches, but not for any other search.

This seems to be a problem in MBS, because a direct query to the search server (http://search.musicbrainz.org/ws/2/artist/?fmt=json&query=artist%3AOlyam&type=artist&limit=25) does work.