owa-mcp

A Model Context Protocol (MCP) server that gives Claude Code full access to your Microsoft Outlook calendar and email — without requiring an Azure app registration.

How it works

The server drives a dedicated, persistent Google Chrome browser via chrome-devtools-mcp, using its own Chrome profile (kept separate from your daily-driver Chrome) so the login session survives across restarts. It navigates that browser to Outlook Web (outlook.office.com) and watches the network requests it makes. When Outlook Web loads, it issues Bearer tokens for its own internal API calls; this server intercepts those tokens and reuses them against the outlook.office.com/api/v2.0 REST endpoint.

The result: full Calendars.ReadWrite and Mail.ReadWrite scope with no OAuth app registration, no client ID, and no IT involvement — as long as you can sign in to Microsoft 365 in the automation browser.

Tokens expire after ~80 minutes. Rather than relaunching a browser for every refresh, the server keeps a single chrome-devtools-mcp connection (and its browser) alive across acquisitions and simply re-navigates to Outlook Web to trigger a fresh token request. The Chrome window is visible (never headless) from the moment the browser first starts, so it's there for you to sign in whenever needed. If no active session is found within 60 seconds, the request fails with a message asking you to sign in and retry — because the connection stays alive, you can take as long as you need (MFA included) and just retry once done, without losing the browser session.

Related MCP server: Outlook MCP Server

Why this approach

Many enterprise Microsoft 365 tenants enforce Conditional Access policies that block third-party OAuth flows (e.g., Azure CLI, custom app registrations) on managed devices. The browser-session interception approach works because it piggybacks on an authentication flow that already satisfies those policy requirements — the same one used by Outlook Web itself. This has been confirmed working with Chrome SSO in at least one Conditional-Access-enforced corp environment; whether it works in yours depends on your organization's specific policies.

Prerequisites

• macOS (tested on macOS 15)

• Google Chrome installed

• chrome-devtools-mcp available via npx — verify with npx chrome-devtools-mcp@latest --version; the server spawns it automatically on first use, no manual setup needed

• Signed in to Microsoft 365 (the first token request opens a visible Chrome window — sign in there if prompted)

• Node.js 20+

Installation

claude mcp add owa -s user -- npx owa-mcp

That's it. Restart Claude Code — you should see calendar tools available.

git clone https://github.com/benpeter/owa-mcp
cd owa-mcp
npm install
npm run build
claude mcp add owa -s user -- node /absolute/path/to/owa-mcp/dist/index.js

Available Tools

get_calendar_events

Returns calendar events in a time range.

create_calendar_event

Create a new event. Adding attendees auto-sends invitations.

update_calendar_event

Update fields on an existing event. Only include fields to change.

cancel_calendar_event

Cancel a meeting you organized. Sends cancellation with reason to attendees. Supports recurring series operations.

delete_calendar_event

Remove an event from your calendar silently (no notification sent). Supports recurring series operations.

respond_to_calendar_event

RSVP to a meeting: accept, tentatively accept, or decline. Uses OWA's internal service.svc API when possible, which works even when the organizer has disabled response requests (ResponseRequested: false). Falls back to the standard REST API if the internal API can't resolve the event.

follow_calendar_event

Track an event on your calendar without RSVPing. Shows as Free, organizer not notified.

get_series_master

Inspect the master event of a recurring series. Returns recurrence pattern, cancelled occurrences, and full event details. Accepts any event ID from the series.

list_series_instances

List all occurrences of a recurring series within a date range. Accepts any event ID from the series.

list_mail_folders

List all mail folders in the mailbox, or child folders of a specific folder.

get_emails

Get emails from a specific mailbox folder with optional filtering.

search_emails

Search emails using full-text query OR structured filters (mutually exclusive).

get_email

Read a single email with full body content and attachment metadata.

get_attachment

Download an email attachment to disk.

send_email

Compose and send a new email in one step. For more control, use create_draft + update_draft + send_draft.

create_draft

Create a new email draft saved to Drafts folder.

create_reply_draft

Create a draft reply to the sender. Returns draft with pre-filled recipients, quoted body, "RE:" subject.

create_reply_all_draft

Create a draft reply-all. Returns draft with all original recipients, quoted body, "RE:" subject.

create_forward_draft

Create a draft forward. Returns draft with quoted body, "FW:" subject, no To recipients.

update_draft

Modify a draft before sending. Can change subject, body, recipients, importance.

send_draft

Send a draft message. Moves from Drafts to Sent Items.

move_email

Move a message to a different folder. Returns the moved message (with updated ID).

delete_email

Delete a message (moves to Deleted Items).

update_email

Update email properties: mark as read/unread, flag/unflag.

Example prompts:

• "What meetings do I have next week?"

• "Create a 30-minute meeting with Jane tomorrow at 2pm"

• "Decline the ECCN sync with a note that I'm on vacation"

• "Follow the Analytics Tech Call so I can see it on my calendar"

• "Cancel all future occurrences of the weekly sync starting from next week"

• "What's the recurrence pattern for the Monday standup?"

• "Create a weekly team sync every Tuesday at 10am for the next 3 months"

• "Show me unread emails from today"

• "Reply to that email from Sarah and add Bob to CC"

• "Forward the Q3 report to the finance team"

• "Mark all emails from the newsletter as read"

Recurrence Object

Used by create_calendar_event and update_calendar_event to define recurring events.

{
  "recurrence": {
    "pattern": {
      "type": "weekly",
      "interval": 1,
      "daysOfWeek": ["Monday", "Wednesday", "Friday"]
    },
    "range": {
      "type": "endDate",
      "startDate": "2026-04-07",
      "endDate": "2026-07-07"
    }
  }
}

Pattern types: daily, weekly, absoluteMonthly, relativeMonthly, absoluteYearly, relativeYearly

Range types: endDate, numbered, noEnd

Troubleshooting

Token acquisition times out / no active session found The automation Chrome window is already open (it becomes visible as soon as the browser starts, not just on timeout) and has navigated to Outlook Web. Switch to it and sign in there (MFA included) at your own pace, then simply retry the request — the browser connection is kept alive, so the same session is reused and you won't need to sign in again on subsequent calls.

ErrorAccessDenied on calendar API The intercepted token didn't carry calendar scope. This is rare; try quitting any Chrome windows using the automation profile (~/Library/Application Support/owa-mcp/chrome-profile) and retrying — the server will relaunch it automatically.

License

Apache 2.0 — see LICENSE.