The interface for adding an event to the calendar has a space for a URL–and it shows up very nicely in the display in Discourse, but when a user saves the event to their own calendar (via the three dots on the top right of the event), no URL is included.
Similarly, it seems that there ought to be a way to include a brief description of the event that would be exported to the user’s calendar. I know I can add more description in the post, but the user would have to go back to Discourse to see it.