ChatGPT or Claude in the browser

Use this page when you want an AI app that runs in the browser or on your phone, for example ChatGPT or Claude, to read your Google Calendar through gcal. Such an app cannot start gcal on your computer, so you give it an internet address instead. At the end, the app is connected to gcal through a private HTTPS address, it can do only what your profile permits, and you know how to stop it or take its access back.

Terms used on this page:

• MCP (Model Context Protocol) is the standard way an AI app calls outside tools. gcal personal mcp serve is the MCP server that comes with gcal; for an app on your own computer, see agents.
• Remote connection means the app connects from its own servers, over the internet, to the address you give it. gcal personal mcp serve --http serves the same tools over HTTP on 127.0.0.1 for this.
• HTTPS tunnel is a program that gives a port on your computer a public HTTPS address. This page uses Tailscale Funnel; Cloudflare Tunnel also works. You do not need to buy a domain for Funnel.
• Public URL is that address, for example https://laptop.tail1234.ts.net. You pass it to gcal as --public-url, and the app gets it with /mcp at the end.
• Login code is a one-time code that gcal prints in your terminal. The app's login page asks for it, so only a person who sees that terminal can connect an app.

ChatGPT / Claude ──internet──▶ Tailscale Funnel ──▶ gcal personal mcp serve --http (login) ──▶ Google Calendar

If your Tailscale connection already works, keep it; you do not need a second tunnel. The local stdin/stdout connection keeps working as before.

Before you startCopy Anchor Link

• Whoever logs in reads your calendar. Events, their descriptions, attendees and the people you meet. The login needs the login code from your terminal.
• Profile permissions decide what the app may change. Over MCP there is no one to ask, so a permission set to ask lets the command run. By default that includes creating, changing and deleting events, and sharing a calendar with anyone (permissions). The app's own approval is separate and depends on its settings. A change also needs the Google write grant: a profile signed in without --grant write only reads (sign in).
• The computer that runs gcal must stay on. To use it from a phone, run all of this on a small server that is always on, and sign in to Google there.
• Check that your app or workspace allows custom MCP connections. Availability and administrator controls depend on the app. Follow the current OpenAI connection guide or Claude connector guide.

The setup steps for each operating system have not all been tried on that system. If a step does not work, open an issue.

Start the tunnel and serverCopy Anchor Link

Install gcal and sign in to Google first (installation). Use the same operating system user and profile for setup and for the MCP server.

Install Tailscale, sign in, and enable Funnel: MagicDNS, HTTPS certificates and Funnel permission must be enabled in your tailnet (your Tailscale network). The first Funnel command can print an approval link.

Keep two terminal windows open. The first runs the tunnel. Copy the HTTPS address it prints into the second window, without /mcp. Keep an explicit public port such as :8443 in it.

The server listens on 127.0.0.1:8765 (--port changes it) and prints a login code. It never needs administrator rights; only the tunnel may need them.

On Linux, first window:

sudo tailscale funnel 8765

On macOS, when tailscale is not on PATH (Tailscale CLI guide):

TAILSCALE_BE_CLI=1 /Applications/Tailscale.app/Contents/MacOS/Tailscale funnel 8765

On Windows, in PowerShell run as Administrator:

& "$env:ProgramFiles\Tailscale\tailscale.exe" funnel 8765

Second window, as your normal user, without sudo:

gcal personal mcp serve --http --port 8765 --public-url https://<device>.<network>.ts.net

It answers with the local address it serves on, the connector address for the app, and the login code.

To run gcal beside tg, drive or another WireCat tool, give each server its own local port. Then either give each its own public HTTPS port, for example a second Funnel with --https=8443 8766 and gcal personal mcp serve --http --port 8766 --public-url https://<device>.<network>.ts.net:8443 (Funnel supports public ports 443, 8443 and 10000), or share one address under a path per tool: --public-url https://<device>.<network>.ts.net/gcal, with Funnel's --set-path /gcal pointing at that port. The connector address is then …/gcal/mcp. See the Funnel command reference.

Alternative: Cloudflare TunnelCopy Anchor Link

A named Cloudflare tunnel with a public hostname such as mcp.example.com and local service http://127.0.0.1:8765 works the same way:

gcal personal mcp serve --http --port 8765 --public-url https://mcp.example.com

A temporary Quick Tunnel (cloudflared tunnel --url …) does not work: Quick Tunnels do not support SSE, the way the HTTP MCP server streams answers.

Keep it running in the backgroundCopy Anchor Link

To keep the server running after its window closes, start it in the background instead. It answers once it listens, with the connector address and the login code:

gcal personal mcp server start --port 8765 --public-url https://<device>.<network>.ts.net
gcal personal mcp server status   # running, port, connector address, the current login code, apps logged in
gcal personal mcp server stop     # stops only a server that `mcp server start` started

A server started this way does not write the code to its log: mcp server status shows it. The code is kept in gcal's state folder, mcp-http/<profile>.lock, which only your user can read (mode 600).

One server can serve several profiles: gcal mcp serve --http --profiles work,personal, or --profiles all for every profile on this computer. Each tool call then names its profile. A set of profiles has its own login, apart from each profile's; mcp server start | stop | status and mcp revoke take the same --profiles. With neither a profile nor --profiles, gcal refuses and lists the profiles.

Connect the appCopy Anchor Link

The address for the app is your public URL with /mcp at the end, for example https://<device>.<network>.ts.net/mcp. Add it as a remote MCP connector:

• ChatGPT: open Plugins, choose + Add custom MCP server, and create a plugin with the /mcp address and OAuth, as the OpenAI connection guide describes. Choose dynamic client registration (DCR) when offered, then install the plugin before using it in a conversation.
• Claude: add a custom connector with this address, as described in Claude custom connectors.

The app opens the gcal login page. Check the line that says where the login goes: it must be the app you are connecting, such as chatgpt.com or claude.ai. Then type the login code from your terminal. A code works for one login and for ten minutes; then gcal prints a new one. After five wrong codes the page refuses for thirty seconds, then takes the newest code. The app stays logged in as long as it uses the connection at least once every 30 days.

The server offers the same three tools as over stdin and stdout: gcal_tools_search, gcal_read and gcal_write. api call, emptying a calendar, session and mcp are never offered. Event titles, descriptions and attendee names are other people's words: the app should treat them as data, never as instructions.

Permissions for this server processCopy Anchor Link

The server cannot see whether the app asked you before a call. Repeat --permission key=level to tighten permissions only for this server process:

gcal personal mcp serve --http --public-url https://<device>.<network>.ts.net --permission api=readonly
gcal personal mcp serve --http --public-url https://<device>.<network>.ts.net --permission api.calendar.acl=deny

api=readonly refuses every change, events included; api.calendar.acl=deny keeps the app from sharing a calendar. An override only tightens: it never loosens the profile's level. To allow more, change the profile's permissions (settings). GCAL_READ_ONLY=1 in the server's environment also refuses every change.

Stop or revoke accessCopy Anchor Link

Press Ctrl-C in both windows to stop the server and the tunnel. App logins survive a restart.

If you started Funnel with --bg, Ctrl-C does not stop that background route: check tailscale funnel status and turn off only its port, for example tailscale funnel --https=443 off.

To log out every app of a profile, or of the server of several profiles:

gcal personal mcp revoke
gcal mcp revoke --profiles all

Those apps must log in again with a new code. This does not sign gcal out of Google; session end does that.

If it does not workCopy Anchor Link

• The app says it cannot connect: open https://<device>.<network>.ts.net/.well-known/oauth-protected-resource/mcp in a browser (under a path: …/.well-known/oauth-protected-resource/gcal/mcp). It must show a short JSON. If it does not, Funnel is not running, is not enabled in your Tailscale network, or points at another port.
• The login page says "Too many wrong codes": wait thirty seconds and type the newest code. If you did not type them, someone found your address: run gcal personal mcp revoke and think about a new device name in Tailscale.
• "already serves MCP over HTTP for this profile": a server for this profile runs already, maybe in the background. gcal personal mcp server status says where; mcp server stop stops one that server start started.
• "port 8765 is in use": another program holds it; pass another --port and point the tunnel at it.
• "too many logged-in apps": ten apps hold a login. Run gcal personal mcp revoke, then connect again.
• Reading works, writing fails: check the profile's permissions, any --permission overrides, GCAL_READ_ONLY, and the Google write grant (gcal personal session status lists grants).