Wikimedia Bugzilla is closed!

Go to Special:ApiSandbox, select a action with generator like setnotificationtimestamp. Choose a generator like backlinks, input a gbltitle like "Main Page" and press "Make request"

The url is /w/api.php?action=setnotificationtimestamp&format=json and the post data is generator=backlinks, so the gbltitle is missing in the post part.

It is also missing in the hash part of the url, so it looks like the whole box from the generator is not taken when building the request.

http://en.wikipedia.org/wiki/Special:ApiSandbox#action=setnotificationtimestamp&format=json&generator=backlinks

No need to give a hint about the usefulness of this request, it is just to demonstrate. You can also use other actions with a generator (purge, watch) except query, which seems to work.