Connecting MCP to Clients — Model Context Protocol

One server, many clients. Here's the exact config for the big three.

Claude Code

claude mcp add github -- npx -y @modelcontextprotocol/server-github

Or edit .mcp.json in your project root:

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "..." }
    }
  }
}

Check what's connected with claude mcp list.

Cursor

Settings → MCP → Add new MCP server, then fill in:

Name: github
Type: command
Command: npx -y @modelcontextprotocol/server-github

(Access tokens go in the env/secret fields.)

Codex CLI

Add to ~/.codex/config.toml:

[mcp_servers.github]
command = "npx"
args = ["-y", "@modelcontextprotocol/server-github"]
env = ["GITHUB_PERSONAL_ACCESS_TOKEN=..."]

Verify it worked

Ask each client a question that requires the tool:

How many open issues does the repo "owner/repo" have?

If the client can answer, the server is connected and the model is actually calling it.

Troubleshooting checklist

Is the server runnable by hand? (npx -y @modelcontextprotocol/server-github shouldn't crash.)
Are paths absolute? Clients don't always inherit your shell's $PATH or cwd.
Did you restart the client after editing config?
Is the API key in env, not in the command string?

.mcp.json checked into a repo is the modern pattern — your whole team gets the same tools automatically.