This seems a fairly obvious public counterpart of
polkit_action_description_get_annotation, and it is used in pkaction.c
in what is pretty much an example of public API use.
https://bugs.freedesktop.org/show_bug.cgi?id=63573
polkit_action_description_get_implicit_inactive
polkit_action_description_get_implicit_active
polkit_action_description_get_annotation
+polkit_action_description_get_annotation_keys
<SUBSECTION Standard>
PolkitActionDescriptionClass
POLKIT_ACTION_DESCRIPTION