How to prevent double booking of events in a Microsoft Graph API meeting room calendar?

Question

I am using Microsoft Graph API to create events in a meeting room calendar, and I have set the 'allowNewTimeProposals' tag to false, the 'showAs' tag to busy, and the 'isAllDay' tag to false. However, I have noticed that I am still able to create multiple events at the same time slot without receiving any error message from the API. This results in conflicts and double bookings. Is there a way to ensure that the API returns an error if a time slot is already occupied by another event in the calendar? (all of that in one API Call)

POST https://graph.microsoft.com/v1.0/users/<UserId>/calendars/<calendarID>/events 
Authorization: Bearer {{token}}
Content-type: application/json 

Body Request:

{
  "subject": "ONE PUNCH MAN PT7",
  "body": {
    "contentType": "HTML",
    "content": "1000 pull-ups?"
  },
  "start": {
    "dateTime": "2023-04-11T18:05:00",
    "timeZone": "Romance Standard Time"
  },
  "end": {
    "dateTime": "2023-04-11T18:15:00",
    "timeZone": "Romance Standard Time"
  },
  "location": {
    "displayName": "<MeetingRoomName>",
    "locationUri": "<MeetingRoomName>@<organizationName>.io",
    "locationType": "conferenceRoom",
    "uniqueId": "<MeetingRoomName>@<organizationName>.io",
    "uniqueIdType": "directory",
  },
  "attendees": [
    {
      "emailAddress": {
      "address":"<MeetingRoomName>@<organizationName>.io",
      "name": "<MeetingRoomName>"
      },
      "type": "resource"
  }
  ],
  "organizer": {
        "emailAddress": {
          "name": "<MeetingRoomName>",
          "address": "<MeetingRoomName>@<organizationName>.io"
        }
  },
  "allowNewTimeProposals": false,
  "showAs": "busy",
  "isAllDay": false,
}

Answer 1

Hi @Cedric Vinci ,

Outlook client/web allows double booking i.e., allows to book/create event more than 1 appointment with same participants at same time, and while booking it will show the availability of the participants as tentative/unavailable but still allows to send invite.

You can however use calendar-getschedule to know free/busy availability information for a collection of users, distributions lists, or resources (rooms or equipment) for a specified time period.

POST https://graph.microsoft.com/v1.0/me/calendar/getSchedule   
Prefer: outlook.timezone="Pacific Standard Time"  
Content-Type: application/json  
  
{          
    "schedules": ["******@contoso.onmicrosoft.com", "******@contoso.onmicrosoft.com"],  
    "startTime": {  
        "dateTime": "2019-03-15T09:00:00",  
        "timeZone": "Pacific Standard Time"  
    },  
    "endTime": {  
        "dateTime": "2019-03-15T18:00:00",  
        "timeZone": "Pacific Standard Time"  
    },  
    "availabilityViewInterval": 60  
}

Additional references findmeetingtimes.

Hope this helps,

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have further questions about this answer, please click "Comment".