An RSVP can carry exactly three values: yes, no, or maybe. That tiny vocabulary — plus a 30-year-old text format called iCalendar — is the entire reason a calendar owned by an AI agent can host meetings that real people accept in Google Calendar, Microsoft 365, and Apple Calendar without any of those clients knowing (or caring) that the other participant is software.
Nylas Agent Accounts — programmatic mailboxes currently in beta — each ship with a real calendar. There's no Google integration, no Microsoft Graph adapter, no per-provider code. The interop happens at the protocol layer, and it's worth understanding how.
The protocol nobody had to invent
When an Agent Account creates an event, the invitation goes out as an ICS REQUEST. When it cancels one, participants get an ICS CANCEL. When it responds to an invite, the organizer receives an ICS REPLY. Every major calendar client already speaks this dialect, which is why an agent's events look native everywhere: there's nothing to translate.
That's the whole trick. Calendar interop isn't an API problem; it's an email problem. Invitations, updates, and responses travel as messages between mailboxes, and since every Agent Account is a real mailbox with a primary calendar attached, it participates in that exchange like any colleague would.
