AddCal MCP server

AddCal MCP Server

A remote Model Context Protocol server for AddCal. Connect Claude, ChatGPT, Cursor or any MCP client and manage the calendars other people subscribe to.

https://addcal.co/mcp

No install, no API key. It is a hosted streamable HTTP server and authentication is OAuth.

This is not a Google Calendar MCP

Almost every calendar MCP server does the same job: it reads and writes your own schedule. Useful, and well covered already.

AddCal is the other side of the calendar. It manages the events you publish for an audience: a class timetable, a fixture list, a release schedule, a conference programme. The people receiving those events never get an invite. They subscribe to a feed, or they click an add-to-calendar link, and the event lands in whichever calendar app they already use.

That difference shows up in the tools. There is no accept-invite, because nobody is invited. There is list-subscribers, get-analytics and create-calendar-collection, because the questions you ask about a published calendar are how many people follow it and whether anyone actually added the event.

Use a Google Calendar MCP to run your day. Use this one to run a calendar other people follow.

Quick start

Pick your client. Cursor and VS Code install in one click.

Claude Code

claude mcp add --transport http addcal https://addcal.co/mcp

Then run /mcp inside Claude Code to sign in.

Claude Desktop and claude.ai

Settings, Connectors, Add custom connector, then paste https://addcal.co/mcp. Custom connectors need a paid plan.

ChatGPT

Settings, Apps & Connectors, Advanced, turn on Developer mode, then add https://addcal.co/mcp as a connector. Requires a paid plan on the web app.

Anything else

Any client that speaks streamable HTTP with OAuth. Windsurf, Goose, Zed and the JetBrains AI Assistant all take a remote MCP URL.

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

Authentication

OAuth 2.1 with PKCE and dynamic client registration. There is no API key to copy and paste.

Your client registers itself, you approve it in a browser, and it receives a token scoped to your team. It can reach exactly what you can reach, no more. Revoke any connected client from Settings, API.

What you can ask for

What have I got on next week?
Create a team standup every weekday at 9am and show me the dates first.
Who has RSVPed yes to the launch party?
Duplicate last month's workshop into March.
Which of my events got the most add-to-calendar clicks?

Tools

19 tools. RO is read only. Required parameters are marked *.

Search

One call across calendars, collections, events and RSVPs, returning the ids every other tool needs. Start here whenever something is named rather than identified.

Calendars

Collections

Shortened. The full README is on GitHub.