To get free/busy information from users calendars (https://docs.microsoft.com/en-us/graph/api/calendar-getschedule?view=graph-rest-1.0&tabs=http), the API permissions Calendars.Read or Calendars.Read...
ericcan one of the issues we were facing also with Calendars.Read was that it is also giving visibility into appointments that are set to "private". One of the reasons why I was asking for something more granular that would only give visibility into free/busy schedule