ms365-mcp

A Microsoft 365 MCP server that's small enough you forget it's running. 67 tools across Teams, Outlook, Calendar, SharePoint, and OneDrive. Built in Zig — no Node, no Python, no runtime dependencies. Statically linked.

The numbers that matter (measured, not estimated):

Metric	Value
Cold-start RAM	1.3 MB peak / 1.9 MB resident
Cold-start time	~120 ms
Binary size	5.9 MB statically linked
list-emails payload to the model	4.2 KB vs 31 KB raw Graph (~87% smaller)
Tokens per list-emails call	~1,050 vs ~7,800 raw
End-to-end test count, against live Graph	94 (no mocks)

The context savings are the lever. On a 200K-token model, ms365-mcp lets the agent hold ~50 inbox snapshots in working memory instead of ~6. That's the difference between "the agent forgot what it was doing" and "the agent finishes the task."

Non-technical readers: see docs/sales-agent-capabilities.md for a one-page tour of what the tool unlocks.

Install

curl -fsSL https://raw.githubusercontent.com/currenthandle/ms365-mcp/main/install.sh | sh

Downloads the right binary for your platform (macOS/Linux, ARM64/x86_64) to ~/.local/bin/ms365-mcp.

Setup

1. Create a Microsoft Entra app registration with delegated permissions for the Graph API scopes you need.

2. Add to your MCP client config (.mcp.json, Claude Desktop, etc.):

{
  "mcpServers": {
    "ms365": {
      "command": "$HOME/.local/bin/ms365-mcp",
      "env": {
        "MS365_CLIENT_ID": "your-client-id",
        "MS365_TENANT_ID": "your-tenant-id"
      }
    }
  }
}

3. The server authenticates via OAuth device code flow — the LLM will call login and prompt you to visit a URL.

Tools

Email (15) — list-emails, read-email, send-email, reply-email, reply-all-email, forward-email, search-emails, list-mail-folders, mark-read-email, move-email, list-email-attachments, read-email-attachment, download-email-attachment, delete-email, batch-delete-emails

Drafts (7) — create-draft, send-draft, update-draft, delete-draft, add-attachment, list-attachments, remove-attachment

Calendar (8) — list-calendar-events, get-calendar-event, create-calendar-event, update-calendar-event, delete-calendar-event, find-meeting-times, get-schedule, respond-to-event

Teams Chat (7) — list-chats, search-chats, list-chat-messages, search-chat-messages, send-chat-message, create-chat, delete-chat-message

Teams Channels (9) — list-teams, list-channels, search-channels, list-channel-messages, get-channel-message-replies, post-channel-message, reply-to-channel-message, delete-channel-message, delete-channel-reply

SharePoint (9) — search-sharepoint-sites, list-sharepoint-drives, list-sharepoint-items, search-sharepoint-files, upload-sharepoint-file, upload-sharepoint-content, create-sharepoint-folder, delete-sharepoint-item, download-sharepoint-file

OneDrive (6) — list-onedrive-items, search-onedrive-files, upload-onedrive-file, upload-onedrive-content, download-onedrive-file, delete-onedrive-item

Auth & utility (6) — login, verify-login, get-mailbox-settings, sync-timezone, search-users, get-profile

Build from source

Requires Zig 0.16.0.

zig build -Doptimize=ReleaseSafe

Run unit tests:

zig build test

Run the live-Graph end-to-end suite (85 tests; needs MS365_CLIENT_ID / MS365_TENANT_ID configured plus the E2E_* variables in .env):

zig build e2e

The e2e harness exercises every tool against real Graph endpoints — including 6 cross-tool user journeys (search a person → open a chat → send → search index → delete → verify gone).