Event template tags provided in the Google Calendar Pro add-on:

Tag usageOutputOptional attributes
[attachments]A list of the event's attachments, if any.-
[attendees]A list of the event's attendees/participants.photo="hide" if you want to hide the attendees avatars.
email="show" to link the attendee name to his/her email.
rsvp="show" to show the RSVP response status of an attendee.
response="yes" to filter attendees by response (yes/no/maybe).
[organizer]Information about the event organizer.photo="hide" if you want to hide the organizer avatar and only show the name.
email="show" to link the organizer name to his/her email.