"An agent joins an event/group with participants/friends at a location.

Related actions:

RegisterAction: Unlike RegisterAction, JoinAction refers to joining a group/team of people.
SubscribeAction: Unlike SubscribeAction, JoinAction does not imply that you'll be receiving updates.
FollowAction: Unlike FollowAction, JoinAction does not imply that you'll be polling for updates

." . . "Join action" . .