The API is made to make automation around calendaring tasks easy. You can pull up appointments, see who booked them, and manage their state. (https://developers.google.com/calendar/overview)

Tracking activity in activity planning software isn't quite as nefarious as looking at peoples emails. Pulling up the meeting bookers boss and sending an email to them & legal is pretty bog standard integration work.

As stated, I can't see any requirement for a client-side footprint...