to find the country at XXX,YYY. It didn't always return a result and it seems it is coastal areas for which this happens. The description of the service says that I should append &radius=RRR but this doesn't seem to work. Eg
(XXX,YYY) = (18.486510, -64.583385)
is a point on the coast of the British Virgin Islands and the service returns
'{"status":{"message":"we are afraid we could not find a administrative country subdivision for latitude and longitude : 18.48651,-64.583385","value":15}}'
and adding &radius=2.0 and/or &radius=20.0 gives exactly the same thing.
If it is helpful we could add the country information to the country subdivision service for those regions where we have country information but no subdivision information. The elements countryCode and countryName would be filled for these regions and the admin elements would be missing.