Outlook CalendarConnect multiple Outlook calendars to Claude
An MCP connection to Outlook Calendar carries one account. If your meetings sit in a work calendar and a personal one — or one per client — one connection is not enough. Switching means authorizing again, and the previous account is gone until you switch back. Handling several accounts of the same connector is an open request on GitHub (anthropics/claude-code #27302).
This guide uses ProxyLoom to put several Outlook Calendar accounts behind a single MCP connection, so Claude can work in any of them and you say which one by name. It takes about five minutes, with no app registration and no JSON config.
What you end up with
One connector in Claude called ProxyLoom. Behind it, each Outlook Calendar account you connected, with a label you chose (for example work, personal, client-a). Every Outlook Calendar tool Claude sees carries an account argument, so "what is on work tomorrow" and "book the review in client-a" both work in the same conversation, without disconnecting anything.
1. Sign up for ProxyLoom
Create an account at https://app.proxyloom.dev/sign-up.
2. Connect each Outlook Calendar account
Signing in puts you on the Connections screen. Click + Connect an account, pick Outlook Calendar, and click Authenticate and connect →. Outlook Calendar's own consent screen opens; approve the access. Repeat for each account you want. Each one becomes a separate connection with its own token.
Back on the Connections screen, give each connection a label: click Add a label in that connection's Label column. The label is the name you will use when you talk to Claude, so use what you already call it:
work,personal,client-a. Without a label ProxyLoom falls back to the name Outlook Calendar reports for the connected account.3. Add ProxyLoom to Claude
In Claude, open Settings → Connectors and click Add (top right). The Add custom connector dialog opens: give it a name — ProxyLoom — paste your ProxyLoom URL as the MCP server URL, and continue. The URL sits in the MCP Endpoint bar at the top of ProxyLoom's Connections screen, with a copy button next to it.
Continuing opens ProxyLoom's authorization in your browser: sign in once and approve, and the connector is authorized. That is the only connection Claude holds.
This works the same in the Claude desktop app, claude.ai and Claude Code. Any client that speaks Streamable HTTP MCP and OAuth 2.1 (Codex, Cursor, ChatGPT) is set up much the same way, with the same URL.
4. Use it
Ask Claude to list the connected accounts to confirm everything is there:
Which Outlook calendars do you have?
Claude asks ProxyLoom and answers with the labels. From then on, name the account in the request:
What is on work tomorrow, and does anything clash with personal?
Book a 30-minute review in client-a on Friday morning.
If a request is ambiguous, Claude asks which account you mean rather than guessing. Which account was used is recorded in ProxyLoom's audit log, so you can check afterwards.
Notes
- There is nothing to set up on the Outlook Calendar side. Each connection carries only what you approved on Outlook Calendar's consent screen: listing calendars and events, expanding a date range into occurrences, creating, changing and deleting events, responding to invitations, and reading free/busy. You can revoke that grant at any time — delete the connection on ProxyLoom's Connections screen, or remove ProxyLoom in the app permissions of your Microsoft account.
- Adding a account later does not mean repeating step 3, Add ProxyLoom to Claude — that one is done once and never again. Connect it on ProxyLoom's Connections screen, and Claude sees it from then on.