Tagging cloud tenants via REST API

It doesn’t appear to be possible to tag cloud tenants via the REST API. The following returns a 404:

It’s possible however to show the tags of a cloud tenant using:

Am I missing something obvious? Is there another way?

There is a statement at the bottom of http://manageiq.org/docs/reference/latest/api/reference/providers which may indicate that what I am trying to achieve is not possible, but I don’t really understand why.

When managing providers of provider provider_class, Tagging and Policy management does not currently apply. So requests including the tags, policies and policy_profiles subcollections will be rejected.