AddCal

What the AddCal MCP server does

The AddCal MCP server gives an AI client access to calendars that an audience follows. It is designed for publishing schedules such as classes, sporting fixtures, product releases, conferences, and other public programmes. Subscribers use feeds or add-to-calendar links in their existing calendar applications; they are not managed as invitees to the publisher’s personal calendar.

The tools cover the main publishing workflow. You can find existing records, create calendars and collections, add or revise events, inspect subscribers and RSVPs, send event invitations, and review usage data. Calendar collections group multiple calendars behind one public page and subscription link.

How it works

AddCal exposes a hosted MCP endpoint at https://addcal.co/mcp using streamable HTTP. An MCP client connects to that URL and authenticates through OAuth 2.1 with PKCE and dynamic client registration. After browser approval, the client receives access scoped to the team and account permissions available to that user.

The search tool can locate calendars, collections, events, and RSVPs when the caller has a name or phrase but not an identifier. Event operations accept dates, time zones, descriptions, locations, all-day flags, RSVP settings, reminders, and recurrence information. Recurrence rules use RFC 5545 syntax without the RRULE: prefix. Use the date-preview tool before creating a recurring series when the generated schedule needs checking.

Setup and configuration

The AddCal MCP server does not require a local package, process, or API key. Add the remote URL as an HTTP MCP connection in a compatible client, then complete the OAuth sign-in flow in a browser. Claude Code can register it with claude mcp add --transport http addcal https://addcal.co/mcp. Claude Desktop and claude.ai use a custom connector, while Cursor and VS Code provide installation links in the project documentation.

A generic client configuration uses the following shape:

{
  "mcpServers": {
    "addcal": {
      "type": "http",
      "url": "https://addcal.co/mcp"
    }
  }
}

Tools and capabilities

Available operations include:

• Search and list calendars, collections, events, subscribers, RSVPs, and invites.
• Create calendars, collections, events, RSVPs, and event invitations.
• Update, duplicate, or permanently delete events.
• Preview dates produced by a recurrence rule.
• Filter events by search terms, ranges, dates, calendars, teams, and other supported fields.
• Retrieve calendar or event analytics and team usage.

The AddCal MCP server can record an RSVP with custom fields and optionally send a confirmation email. It can also report subscriber and engagement information, including analytics for calendar and event activity where the account plan permits those features.

Limitations and notes

This service is for published calendars, not a replacement for a personal Google Calendar workflow. It does not use an invite-and-accept model for the people who follow a calendar. Subscriber names and email addresses are available only when the calendar requests those details; many subscriber records can therefore be anonymous.

Three operations are marked destructive: sending an event invite, creating an RSVP, and deleting an event. Each requires an explicit confirmation parameter. Invitations and RSVP confirmations email real people, while event deletion is permanent; deleting a recurring event removes the entire series. Clients should ask for approval before invoking these operations.

Features such as collections, calendar invitations, and analytics depend on the AddCal plan. The server follows the account’s existing limits and reports a limit instead of retrying automatically.