MCP in Claude: connectors, Claude Desktop and Claude Code

The short version: in claude.ai and Claude Desktop a remote MCP server is added as a custom connector — paste a URL, sign in, done. In Claude Code it is a single claude mcp add --transport http, or an entry in .mcp.json. Both paths are below, step by step, with live server URLs you can connect right now.

If you have not yet worked out what MCP is and how a remote server differs from a local one, start with the overview of MCP servers — five minutes of reading.

Where MCP is connected in Claude

Path 1. A connector in claude.ai and Claude Desktop

A connector is set up once in your Claude account and then works everywhere you are signed in: in the browser, in Desktop and on your phone.

1. Open Settings → Connectors.
2. Click Add custom connector, give it a name and paste the server URL — for example https://twelver.app/api/mcp/v1/web-search.
3. Click Connect: a sign-in window opens. Sign in to your Twelver account and grant access.
4. In a new chat, open the tools menu and check the connector is on. Ask it something like "search the web for what Claude shipped this week" — Claude will call web-search.

One detail explains almost every "it won't connect" complaint: the connection to the server is made by Anthropic's servers, not by your computer. So a connector can only reach servers that are reachable from the internet — a server on localhost cannot be added this way, and for that you want Claude Code or Claude Desktop with a local configuration.

Path 2. Claude Code: claude mcp add

In Claude Code a remote server is one command. The --transport http flag is required — without it the command waits for a local process.

claude mcp add --transport http twelver-web-search https://twelver.app/api/mcp/v1/web-search
claude mcp add --transport http twelver-image https://twelver.app/api/mcp/v1/image-generation

Then run claude and type /mcp: new servers are marked as needing sign-in. Pick the server, sign in through the browser, and the tools appear in the session. That same /mcp list shows which servers are connected and how many tools each one has.

Where the setting is stored: three scopes

Signing in with a key instead of OAuth

OAuth is convenient, but it needs a browser and a registered account, and the token lives 7 days — after that you sign in again. For a headless server, for CI, or simply for "set it and forget it", a key in the Authorization header is easier. The button below issues one, no registration required:

claude mcp add --transport http --scope user twelver-web-search https://twelver.app/api/mcp/v1/web-search \
  --header "Authorization: Bearer sk-<your-key>"

For a project-level .mcp.json, keep the key out of the file — it will end up in git. Claude Code expands environment variables inside that file, so the key can live in TWELVER_API_KEY:

{
  "mcpServers": {
    "twelver-web-search": {
      "type": "http",
      "url": "https://twelver.app/api/mcp/v1/web-search",
      "headers": {
        "Authorization": "Bearer ${TWELVER_API_KEY}"
      }
    }
  }
}

Slow tools: video generation and timeouts

Search answers in seconds; video generation takes minutes — the server holds the call open until the clip is ready. If Claude Code cuts the call short, raise the timeout for that server with the timeout field (in milliseconds), or for all of them with the MCP_TOOL_TIMEOUT variable:

{
  "mcpServers": {
    "twelver-video": {
      "type": "http",
      "url": "https://twelver.app/api/mcp/v1/seedance-video-generation",
      "timeout": 600000
    }
  }
}

What actually comes back from a generation call, and how to work with it, is covered in image and video generation in Claude.

Build your own set

Tick the tools you want — one connector URL per set appears below. The same URLs can be passed to claude mcp add for Claude Code.

If it does not work

Not only working in Claude? The same scheme for Cursor, Codex and OpenCode.