A calendar for every agent inbox.

Invitations that arrive by email land on the calendar

Most calendars for agents stop at sending. This one reads too. Every inbound message is checked for a text/calendar part, and when one is there the calendar applies it before the message is stored:

• A new invitation (METHOD:REQUEST) creates the event with source: inbound, the sender as organizer, and your inbox listed among the attendees with needs-action. Webhook: calendar.event.created.
• An update to an invitation you already have is matched on its ical_uid and applied in place: new time, new title, new attendee list. Webhook: calendar.event.updated. Stale copies with a lower SEQUENCE are ignored.
• A cancellation (METHOD:CANCEL) marks the event cancelled. Webhook: calendar.event.cancelled.
• A reply (METHOD:REPLY) to an invitation your agent sent records that attendee's accepted, declined or tentative on the event. Webhook: calendar.event.updated.

The message itself carries a compact calendar_event summary so an agent reading its mail sees the event without a second call. action says what the message did to the calendar.

{
  "message_id": "e7a2c9d1-4b8f-4c3e-9d6a-5f1b0c8e2a74",
  "from_email": "dana@example.com",
  "subject": "Invitation: Vendor review @ Tue Sep 22, 2026 11am",
  "calendar_method": "REQUEST",
  "calendar_event": {
    "event_id": "3d7a1f9c-52e4-4b8d-9a6f-1e0c7b2d8f35",
    "inbox_id": "6f1c2d3e-8a4b-4c5d-9e6f-0a1b2c3d4e5f",
    "ical_uid": "7f3a9c1e-2b4d-4e6f-8a0b@google.com",
    "title": "Vendor review",
    "start_at": "2026-09-22T15:00:00Z",
    "end_at": "2026-09-22T15:45:00Z",
    "status": "confirmed",
    "organizer": { "email": "dana@example.com", "name": "Dana" },
    "action": "created"                  // created | updated | cancelled | replied | unchanged
  },
  ...
}

The same summary is the payload of the three calendar.event.* webhooks, so a handler that already routes message.received can subscribe to the calendar events and act on the event rather than re-parsing the mail. Calendar ingestion never loses a message: if parsing fails for any reason, the email is stored as normal and the calendar is simply left alone.

In the SDKs and over MCP

Times are ISO 8601 and need a zone: a trailing Z, an offset, or a timezone argument next to a local time. A bare date makes an all-day event. Everything is stored and returned as UTC instants.

Python

from deadsimple import DeadSimple

client = DeadSimple(api_key="dse_...")

# 1. Put an event on the inbox's calendar. Nothing is sent yet.
event = client.calendar.create(
    inbox_id,
    title="Kickoff: Q4 onboarding",
    start="2026-09-22T11:00:00", timezone="America/New_York",
    duration_minutes=30,
    location="https://meet.example.com/kickoff",
    attendees=["dana@example.com", {"email": "sam@example.com", "optional": True}],
)

# 2. Send it as a real invitation (Accept / Decline in their mail client).
sent = client.calendar.invite(inbox_id, event["event_id"],
                             text_body="Kickoff for the Q4 onboarding project. Agenda attached Monday.")
print(sent["method"], sent["sent_to"], sent["message_id"])   # REQUEST [...] msg_...

# 3. Reschedule: PATCH raises sequence, invite again sends an update, not a duplicate.
client.calendar.update(inbox_id, event["event_id"], start="2026-09-23T11:00:00", timezone="America/New_York")
client.calendar.invite(inbox_id, event["event_id"])

# 4. Answer an invitation that arrived by email.
for ev in client.calendar.list(inbox_id, start_from="2026-09-22")["events"]:
    if ev["source"] == "inbound" and ev["status"] == "confirmed":
        client.calendar.rsvp(inbox_id, ev["event_id"], "accepted", comment="See you then.")

# 5. Hand a human the subscription URL.
feed = client.calendar.feed(inbox_id)
print(feed["webcal_url"])     # webcal://api.deadsimple.email/v1/inboxes/.../calendar.ics?token=...

# Every event on every inbox the key can see:
client.calendar.list_all(start_from="2026-09-21", start_to="2026-09-27")

Node

import { DeadSimple } from "@deadsimple/email"

const client = new DeadSimple({ apiKey: "dse_..." })

const event = await client.calendar.create(inboxId, {
  title: "Kickoff: Q4 onboarding",
  start: "2026-09-22T15:00:00Z",
  duration_minutes: 30,
  attendees: ["dana@example.com"],
})

const sent = await client.calendar.invite(inboxId, event.event_id, {
  textBody: "Kickoff for the Q4 onboarding project.",
})
// sent.method === "REQUEST", sent.sent_to, sent.message_id

// Answer something that arrived by email
const { events } = await client.calendar.list(inboxId, { status: "confirmed" })
for (const ev of events) {
  if (ev.source === "inbound") await client.calendar.rsvp(inboxId, ev.event_id, "accepted")
}

// Feed for a human's calendar app; rotate if the URL ever leaks
const feed = await client.calendar.feed(inboxId)      // feed.feed_url, feed.webcal_url
await client.calendar.rotateFeed(inboxId)

MCP

The hosted MCP server at https://api.deadsimple.email/mcp and the local python -m deadsimple.mcp both expose two calendar tools on top of the existing invite tools, for 19 tools in total.

list_calendar_events(inbox_id, from_date="", to_date="", status="", limit=20)
# Soonest first. Includes every invitation that arrived by email.

create_calendar_event(inbox_id, title, start, end="", duration_minutes=30,
                      timezone="", location="", description="",
                      attendees="", all_day=False, send_invites=False)
# send_invites=True also emails the attendees a real invitation.

# In Claude, Cursor or Grok Bot, that means:
"What is on your calendar this week?"
"Set up a 30 minute call with dana@example.com on Tuesday at 11 New York time and send the invite."

Subscribe a human to the agent's calendar

An agent's schedule is only useful if the people around it can see it. Each inbox has an iCalendar feed that any calendar app can subscribe to. Get the URLs once:

{
  "inbox_id": "6f1c2d3e-8a4b-4c5d-9e6f-0a1b2c3d4e5f",
  "email": "ops_9c4e1f2a@box1.deadsimple.email",
  "feed_url": "https://api.deadsimple.email/v1/inboxes/6f1c.../calendar.ics?token=dsecal_9f3c1a...e7",
  "webcal_url": "webcal://api.deadsimple.email/v1/inboxes/6f1c.../calendar.ics?token=dsecal_9f3c1a...e7",
  "token_created_at": "2026-09-17T14:05:40Z",
  "rotated": true          // true on the first call and after a rotate
}

Google Calendar

1. Open Google Calendar on the web. In the left sidebar, next to Other calendars, click the plus sign and choose From URL.
2. Paste the feed_url (the https one) and click Add calendar.
3. The agent's calendar appears under Other calendars and syncs to the Google Calendar apps on your phone. Google refreshes subscribed calendars on its own schedule, typically every several hours.

Apple Calendar (Mac, iPhone, iPad)

1. Open the webcal_url on the device, or in Calendar on a Mac choose File, New Calendar Subscription and paste it.
2. Pick where to keep it (iCloud makes it available on every device) and set Auto-refresh to every 15 minutes or hourly.
3. Click OK. New events, changes and cancellations arrive on each refresh.

Outlook

In Outlook on the web, choose Add calendar, then Subscribe from web, and paste the https URL. Desktop Outlook accepts the same URL under Open Calendar, From Internet.

Treat the URL as a secret. The token in the query string is the only credential on the feed, and calendar apps fetch it with no API key. If it is pasted somewhere it should not be, call POST /v1/inboxes/{inbox_id}/calendar/feed/rotate (calendar.rotate_feed): the old URL stops answering at once and anyone subscribed to it stops receiving updates. The feed lists confirmed and tentative events only; cancelled ones are dropped so they disappear from subscribers on the next refresh. X-WR-TIMEZONE carries the zone most events were created in, so all-day events and local times render the way you expect.

What it does not do yet

Being clear about the edges saves everyone time.

• No booking page. There is no public link where a human picks a free slot and the event is created for them. Nylas ships this as Scheduler alongside Agent Accounts, and it is a real convenience if your agent's main job is taking bookings. AgentMail has no calendar at all. On Dead Simple the equivalent today is done by email: the agent proposes times in a message, and when the reply comes back it creates the event and sends the invitation.
• No free/busy lookup across other people's calendars. The calendar knows what the agent has been invited to and what it has scheduled. It does not query Google or Microsoft for someone else's availability.
• No recurrence expansion yet. Events are single occurrences. A weekly meeting is one event per week, which the agent can create in a loop; a repeating invitation that arrives by email is stored as one event at its first start, without the rule.
• Feeds are read-only. A human subscribed in Google or Apple Calendar sees the agent's events; editing them there does not write back. Changes go through the API, the SDKs or an MCP tool.

If a booking page would change your decision, tell us. It is the obvious next step and the ordering is driven by who asks.