Claude MCP: how to add an MCP server

Claude MCP means Claude using the Model Context Protocol to call tools outside the chat. In Claude, add an MCP server as a custom connector under Customize, then Connectors. In Claude Code, run claude mcp add --transport http with a name and URL. Below is a real call to our free server, https://www.realworldmcp.com/api/mcp.

What MCP means in Claude

MCP, the Model Context Protocol, is an open standard for connecting AI apps to outside tools and data (modelcontextprotocol.io ↗). Anthropic created it. An MCP server offers tools. Claude is the client that calls them.

• In Claude on the web, desktop and mobile, a remote MCP server is called a connector. You add it by URL as a custom connector.
• In Claude Code, you add servers with the claude mcp command.
• In the Claude API, the MCP connector ↗ lets a Messages API request call a remote server.

One detail matters for remote servers. Claude connects to a custom connector from Anthropic's cloud, not from your computer. So the server must be reachable on the public internet (source ↗). Ours is.

Add an MCP connector in Claude

1. Click Add Real World MCP to Claude ↗. Claude opens Add custom connector with the name and URL filled in. If you are signed out, sign in first.
2. Or add it by hand: go to Customize → Connectors, click + Add, then Add custom connector. Name it Real World MCP and paste the URL below. Click Continue.
3. Under Authentication, pick No sign in. Click Add.
4. In a chat, click +, open Connectors, and turn Real World MCP on.

https://www.realworldmcp.com/api/mcp

Free plans can add one custom connector. On Team and Enterprise plans an Owner adds it first under Organization settings → Connectors → Add → Custom → Web (or with the admin install link ↗); members then click Connect under Customize → Connectors. Claude reaches the server from Anthropic's cloud, so it must be public. Ours is.

Custom connectors are not verified by Anthropic, so only add servers you trust (Anthropic help center ↗).

Add an MCP server in Claude Code

The documented form is claude mcp add --transport http <name> <url> (Claude Code docs ↗). For Real World MCP:

claude mcp add --transport http realworldmcp https://www.realworldmcp.com/api/mcp

By default this uses local scope: only you, only in the current project. To use it in every project, add --scope user:

claude mcp add --transport http --scope user realworldmcp https://www.realworldmcp.com/api/mcp

Then check and manage it. Inside Claude Code, /mcp shows server status.

claude mcp list
claude mcp get realworldmcp
claude mcp remove realworldmcp

Using another client?

ChatGPT, Codex, Gemini, Cursor, VS Code and Windsurf take the same URL. Pick yours:

https://www.realworldmcp.com/api/mcp

https://www.realworldmcp.com/api/mcp

claude mcp add --transport http realworldmcp https://www.realworldmcp.com/api/mcp

codex mcp add realworldmcp --url https://www.realworldmcp.com/api/mcp

https://www.realworldmcp.com/api/mcp

gemini mcp add --transport http --scope user realworldmcp https://www.realworldmcp.com/api/mcp

{
  "mcpServers": {
    "realworldmcp": {
      "url": "https://www.realworldmcp.com/api/mcp"
    }
  }
}

code --add-mcp '{"name":"realworldmcp","type":"http","url":"https://www.realworldmcp.com/api/mcp"}'

{
  "mcpServers": {
    "realworldmcp": {
      "serverUrl": "https://www.realworldmcp.com/api/mcp"
    }
  }
}

{
  "mcpServers": {
    "realworldmcp": {
      "url": "https://www.realworldmcp.com/api/mcp"
    }
  }
}

A real MCP call, step by step

When Claude uses a tool, it sends a JSON-RPC message to the server. You can send the same message yourself. This one asks our server's global_meteor_network.shower_counts tool for the top 3 meteor showers in the Global Meteor Network's latest data.

curl -sS -X POST https://www.realworldmcp.com/api/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"global_meteor_network.shower_counts","arguments":{"top":3}}}'

Claude gets this back. It is the tool's output from our last site build, Nov 1, 2026, trimmed. Over MCP it arrives as JSON and as text, with the source and license line at the end.

{
 "generated": "2026-11-01 19:24:53.491169+00:00 UTC",
 "window": {
  "from": "2026-10-31T19:07:22.811Z",
  "to": "2026-11-01T10:25:42.925Z"
 },
 "total_trajectories": 1233,
 "sporadic": 903,
 "showers": [
  {
   "code": "STA",
   "name": "Southern Taurids",
   "count": 85
  },
  {
   "code": "ORI",
   "name": "Orionids",
   "count": 73
  },
  {
   "code": "DAT",
   "name": null,
   "count": 52
  }
 ],
 "attribution": {
  "source": "Global Meteor Network",
  "license": "CC BY 4.0",
  "source_url": "https://globalmeteornetwork.org/data/",
  "cite": "Vida et al. 2020, MNRAS 491(2); Vida et al. 2021, MNRAS 506(4)"
 }
}

Before calling tools, a client sends initialize and then tools/list to learn what the server offers. Our server answers with search_tools, get_tool and call_tool and 9 featured live tools; everything else is reached through call_tool. The full list is on How it works.

Try it in Claude

After adding the connector, paste a prompt. Claude picks the tool and the arguments itself.

See more in Claude connectors for real-world data and on the tasks pages.