Connect an MCP server to Claude – web, desktop, mobile and developer tools

An MCP server gives an AI assistant tools: read data from a database, create tickets, search files. For Claude on the web, in the desktop app and on your phone to use such a server, the server has to be reachable over the internet and speak Streamable HTTP. This guide shows how to add such a remote server as a "connector" – and how to use the same server in Claude Code, Cursor and VS Code.

What you need first

• The server address, usually ending in /mcp, for example https://example.xenmcp.com/mcp.
• The sign-in method: OAuth (you sign in with the provider and click "Allow"), a fixed key (API key), or no sign-in at all.
• A Claude account. According to Anthropic, custom connectors are available on all plans; the Free plan allows only one custom connector. Menus change from time to time – Anthropic's help center is the reference.

Good to know: Claude connects to your server from Anthropic's cloud, not from your computer. A server that only runs on a company network or behind a VPN is not reachable for Claude unless you make it public or allow Anthropic's IP ranges in your firewall.

Claude on the web and in Claude Desktop (Pro, Max)

1. Open Customize › Connectors (in older versions: Settings › Connectors).
2. Click + Add, then Add custom connector.
3. Enter a name you will recognize in the list.
4. Enter the server address and click Continue.
5. Check the detected sign-in settings. For OAuth, choose for example "Sign in now" under Authentication; for a fixed key, add it under Request headers.
6. Click Add. With OAuth, the server's sign-in window opens: sign in, allow access, done.

In a chat, turn the connector on via the + at the lower left and Connectors. Claude then shows which tools it calls. A good server marks tools that change or delete data as "destructive" – Claude then asks before calling them.

Claude Desktop uses the same connectors as the web version. In addition, Claude Desktop can start local servers from claude_desktop_config.json; these only run on your computer and are not available in the browser or on your phone.

Team and Enterprise

In Team and Enterprise accounts, an Owner adds the connector once for the organization: Organization settings › Connectors › Add, then Custom › Web, enter the address, set the sign-in. Each member then finds the connector under Customize › Connectors, labeled "Custom", and clicks Connect to sign in with their own account.

This is the key difference between OAuth and a fixed key: with OAuth, each person only sees what they are allowed to see, and you can revoke access for individuals. A fixed key under "Request headers" applies to everyone – whoever uses the connector works with exactly those rights. So use a key with as few permissions as possible if you share it.

On your phone

You add new connectors in the browser. In the Claude app for iOS and Android, connectors added to your account are then available – even when your laptop is off, because the connection runs through Anthropic's cloud. Local (stdio) servers do not work on a phone at all. How to bring a local server online is covered in Run a local MCP server remotely.

Claude Code

In Claude Code, add a remote server with one command:

claude mcp add --transport http example https://example.xenmcp.com/mcp

If the server supports OAuth, run /mcp in Claude Code, select the server and sign in in the browser. For servers with a fixed key there is the --header option:

claude mcp add --transport http example https://example.com/mcp --header "Authorization: Bearer YOUR_KEY"

Cursor

In Cursor, add the server to .cursor/mcp.json in the project or to ~/.cursor/mcp.json for all projects:

{
  "mcpServers": {
    "example": {
      "url": "https://example.xenmcp.com/mcp"
    }
  }
}

If the server supports OAuth, Cursor starts the sign-in itself when you enable the server.

VS Code

VS Code (Copilot in agent mode) reads servers from .vscode/mcp.json. For a remote server, type and address are enough:

{
  "servers": {
    "example": {
      "type": "http",
      "url": "https://example.xenmcp.com/mcp"
    }
  }
}

On first start, VS Code opens a browser window for OAuth servers. Enter the address exactly as the provider gives it – even a trailing slash can make a difference.

How the OAuth sign-in works

You don't need to know the details, but they help with troubleshooting:

1. Claude calls the server without credentials and gets a 401 response pointing to the server's metadata.
2. From the metadata, Claude learns where to sign in and registers there as an application.
3. You sign in in the browser and allow access.
4. Claude receives an access token valid for this one server only and repeats the call.

Claude never sees the credentials of your database or service – they stay with the server.

Common problems

• 401 or "Authentication failed": the server expects a sign-in that is not set up, or you forgot a key header. Check the provider's sign-in method.
• Server not reachable: the address is wrong (often /mcp is missing), the server is internal only, or a firewall blocks Anthropic's IP ranges.
• Connector not shown in the chat: it is not enabled for this conversation (+ › Connectors).
• Cannot add another connector: the Free plan allows only one custom connector.
• Tools missing: some servers only list tools after sign-in or depending on your permissions.

And XenMCP?

XenMCP (by Xenaxio) is preparing an MCP hosting service in Germany: each server gets its own address https://<name>.xenmcp.com/mcp with OAuth 2.1, which you add to Claude, Cursor or VS Code exactly as described above. At the start of the closed beta there will be servers for MongoDB, PostgreSQL and MySQL/MariaDB, plus an OAuth bridge for servers that only accept an API key – so each person on the team signs in individually instead of sharing one key. Join the waitlist. Note: what Claude does with the results happens in Anthropic's infrastructure; XenMCP itself runs in Germany.

FAQ

Can I add an MCP server directly on my phone?

Currently no: you add it in the browser, and it is then available in the app. Local servers do not run on a phone.

Do I need a paid Claude plan?

According to Anthropic, all plans can use custom connectors, but the Free plan only one. On Team and Enterprise, an Owner sets up the connector for everyone.

Is OAuth better than an API key in a header?

For teams, yes: each person signs in themselves, sees only their own data and can be removed individually. A key in a header applies to everyone who uses the connector.

Why can't Claude reach my server on the company network?

Because the connection comes from Anthropic's cloud. The server must be publicly reachable, or your firewall must allow Anthropic's IP ranges.