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Claude Code MCP servers: connect your apps to Claude Code

Add Gmail, Slack, Google Calendar, Notion and more to Claude Code with one command, sign in with OAuth, and choose what it may do in each app.

Updated

Short answer

Claude Code reaches other apps through MCP servers: connectors that let it use another app. Add a remote one with claude mcp add --transport http <name> <url>, sign in from /mcp, and its tools appear as mcp__<name>__<tool>. Developer tools like GitHub and Sentry have their own servers. For your email, calendar and Slack, Upsy is one server that holds them all.

What Claude Code connects to natively

Claude Code gets apps three ways: servers you add with claude mcp add, plugins from Anthropic's marketplace, and, if you log in with a Claude subscription, the connectors you added at claude.ai (Claude Code docs).

App Built in? Notes
Gmail No Claude's Gmail connector carries over from claude.ai with a subscription login: one account, attachment metadata only. Google's own server is in developer preview
Google Calendar, Drive No Claude's Google connectors carry over the same way
Slack Plugin Slack's plugin, /plugin install slack@claude-plugins-official. A workspace admin approves the MCP integration
GitHub, Linear, Notion, Sentry, Atlassian Plugin Official plugins in Anthropic's marketplace, each with its own sign-in
Outlook No Claude's Microsoft 365 connector needs a work tenant; outlook.com and Hotmail aren't supported

Where Claude Code keeps a server depends on its scope:

Scope Stored in Loads in Good for
local (default) ~/.claude.json The current project only Trying a server out
project .mcp.json in the repo The project, for everyone who clones it Team tools; each person approves the server and signs in
user ~/.claude.json Every project Your own email, calendar and Slack

Remote servers use HTTP. SSE is deprecated. claude mcp list shows what's configured, and claude mcp remove <name> deletes a server and its stored tokens.

What's missing

  • Personal apps. There's no Gmail, Google Calendar or Outlook plugin in Anthropic's marketplace. The claude.ai connectors fill in only when you log in with a subscription, not with an API key, a provider like Amazon Bedrock, or CLAUDE_CODE_OAUTH_TOKEN.
  • More than one account. Claude's Gmail connector takes one Google account at a time.
  • Personal Outlook. Claude's Microsoft 365 connector takes work accounts only.
  • One place to control and review. Every server signs in on its own. Your Claude Code permission rules don't follow you to Cursor or Codex, and nothing shows what each tool did across apps.
  • Self-hosting overhead. Open-source Gmail and Workspace servers need a Google Cloud project, an OAuth client and a process you keep running.

How Upsy fills the gap

Upsy is one remote MCP server at https://upsy.ai/connect:

  • Your apps in one server: Gmail, Google Calendar, Google Drive with Docs and Sheets, and Slack. Linear, Notion, Atlassian, Sentry, Supabase and other services connect through their own MCP servers, with their own sign-in, and Claude Code reaches them with app_tools, app_read and app_call.
  • Up to five accounts per app, such as work and personal Gmail. The tools take an account argument.
  • Access per assistant: Full access, Read-only, Pick actions (the tools you choose) or No access, enforced by Upsy. Tools Claude Code isn't allowed aren't listed and can't be called.
  • History and alerts: every action is logged under Claude Code, and Upsy emails you when one assistant deletes, sends or reads a lot at once.
  • One setup for every assistant: the same connections work in Cursor, Codex, Claude and ChatGPT, each with its own access.
  • Memory, files and a cloud browser that's signed in to your sites. Upsy's Outlook connector is pending until Microsoft approves Upsy; until then, Claude Code can use outlook.com in that browser.

It works however Claude Code is logged in. If you only need GitHub or Linear in one repo, the vendor's own plugin is simpler. For Gmail details, see connect Gmail to Claude Code. For Slack, including when Slack's own server is the better fit, see connect Slack to Claude Code.

Add Upsy to Claude Code

  1. Sign up free at upsy.ai and connect your apps under Apps.

  2. In your terminal, run:

    claude mcp add --transport http --scope user upsy https://upsy.ai/connect

  3. Start claude, type /mcp, choose upsy and authenticate. On the Upsy page that opens, sign in, choose what Claude Code can use and click Allow.

  4. Run claude mcp list to confirm upsy is connected.

There's no API key: Claude Code signs in with OAuth and refreshes its tokens itself. The address works in any MCP client, as the Gmail MCP server guide shows.

Already added Upsy to Claude at claude.ai? With a subscription login, it shows up in /mcp as a claude.ai connector, with the access you gave Claude. Adding it with claude mcp add gives Claude Code its own access level and its own entries in History. Claude Code connects once per address and prefers the server you added yourself.

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