Identifying Event Creators Across Google, Microsoft, and iCloud

{
  "organizer": { "name": "Alice Chen", "email": "alice@company.com" },
  "creator": null
}    

Key nuances:

• organizer.email is the person the meeting is organized for, not necessarily who pressed "Create." 
• Microsoft Graph does have an isOrganizer boolean that indicates whether the synced user is the organizer of the event. Nylas does not currently expose this field.

Bottom line: For Microsoft, organizer.email is your only option and is reliable for the vast majority of cases.

Google (Calendar API)

What you get: Both organizer and creator, and they often differ.

Google Calendar has the richest ownership model. Both fields are populated:

{
  "organizer": { "name": "Alice Chen", "email": "alice@company.com" },
  "creator": { "name": "Alice Chen", "email": "alice@company.com" }
}

Scenario 1: Shared / Group Calendars

When someone creates an event on a shared Google calendar, organizer becomes the calendar itself (not a person), while creator remains the human:

{
  "organizer": {
    "name": "Engineering Team",
    "email": "c_abc123...@group.calendar.google.com"
  },
  "creator": {
    "name": "Alice Chen",
    "email": "alice@company.com"
  }
}

Scenario 2: External Invites (Cross-Provider)

When a Microsoft user invites a Google user, Google "re-parents" the event. On the Google user's calendar:

• creator.email = the Google user (mailbox owner) — Google claims them as the "creator" of this copy
• organizer.email = the original Microsoft organizer who sent the invite

{
  "organizer": { "name": "External Person", "email": "someone@outlook.com" },
  "creator": { "name": "Local User", "email": "localuser@gmail.com" }
}

{
  "organizer": { "name": "CEO", "email": "ceo@company.com" },
  "creator": { "name": "Executive Assistant", "email": "assistant@company.com" }
}