Related is todo/some way to get a list of options for a special remote of a given type .

At the moment there is no checks in place even for built-in special remotes on either provided special remote options/parameters are not mystyped, and either values of type bool are in correct form (true/false and not on/off etc)? E.g.

$> git annex initremote datasets.datalad.org4 location= type=git mumbojumbo=crap autoenable=ofcause
initremote datasets.datalad.org4 ok
(recording state in git...)

proceeds just fine although one of the options is not anything that special remote would care about, and a bool value for a known one is incorrectly specified (I often missed trailing e in true)

At least for the built in special remotes (not external) this should be possible and would help to avoid issues such as OpenNeuroOrg/datalad-service/issues/67 etc. Ideally parameters verification should also be provisioned in external special remotes protocol.