How to retrieve only meetings?

I want to select only meetings (appointments with multiple people) in MS Graph (not necessarily online meetings). My guess is I would have to filter on the attendees collection not being empty.

• Is that assumption correct?
• How do I do that?

I have tried all kinds of variations on attendees like

https://graph.microsoft.com/v1.0/users/{{UserID}}/calendar/events?$filter=start/dateTime ge '{{start_datetime}}' and end/dateTime le '{{end_datetime}}' and attendees.length ne 0

... but so far no success. (The {{...}} are Postman environment variables). All I get is

"error": {
    "code": "BadRequest",
    "message": "Invalid filter clause",

I have looked at lambda operators, but something like this also is an invalid filter ^**:

https://graph.microsoft.com/v1.0/me/calendar/events?$filter=attendees/any(e:e/emailAddress eq '')

Googling for "ms graph empty collection" gives me plenty of posts for people receiving no results, but that's not what I'm looking for. It also does not help that the terms "appointment" and "meeting" are used interchangeably

<sup>** Follow-up question: https://stackoverflow.com/questions/75554213/are-lambda-filters-on-subproperties-of-calendar-event-collections-allowed&lt;/sup>

Update 24 Feb.:<br />
As pointed out in this answer to that follow-up question I cannot uses attendees. The answer to my initial question Is that assumption correct? is No. Is there anything else I can filter on to retrieve only meetings?

When posting this on 25-02-2023 it is not supported to combine the $filter operator with the $count operator on the attendees property of an event in microsoft graph api.

Seeing as running this query https://graph.microsoft.com/v1.0/users?$filter=assignedLicenses/$count ne 0&$count=true in the online graph exlorer works fine, but doing the same for events like this https://graph.microsoft.com/v1.0/me/events?$filter=assignedLicenses/$count ne 0&$count=true doesn't work. and results in this

{
    "error": {
        "code": "ErrorInvalidUrlQueryFilter",
        "message": "The query filter contains one or more invalid nodes."
    }
}

The microsoft documentation states that if you want support for using the $filter on a not supported property you can request it here