My reading of the sdam spec indicates the following problems in server description query methods (primary? etc.):

1. They do not check for response being successful, thus requiring the calling code to check if a description is unknown before checking if it's anything other than unknown.
2. They consider a response without `ok` field successful.
3. "Other" server description includes unknown and ghost ones. The three should be separate and "other" is not a superset of either ghost or unknown according to my reading of the spec.