Set up the MCP server

The mcpX server is published as @rpx_/mcpx. Your AI client launches it over stdio when it needs browser tools; you do not need to run a separate hosted service.

Requirements

Node.js 20 or newer
npm, included with Node.js
An application that supports local MCP servers

Verify Node.js before continuing:

node --version
npm --version

Add mcpX to your client

Open your client's MCP settings and add:

{
  "mcpServers": {
    "browser-mcpx": {
      "command": "npx",
      "args": ["-y", "@rpx_/mcpx@latest"]
    }
  }
}

Using @latest lets npm resolve the current published version when the client starts a fresh process. For a reproducible team configuration, replace it with an exact version such as @rpx_/mcpx@1.2.1.

Restart and verify

Save the configuration, then restart or reload the client. Confirm that mcpX appears in its MCP server or tools list.

The server listens on loopback for the Chrome extension. It prefers port 3000 and can select an available port through 3010; the official extension discovers the selected port automatically.

Environment options

Most users do not need environment variables.

Variable	Use
`MCPX_PORT`	Force one local port instead of automatic selection. Startup fails if it is occupied.
`MCPX_EXTENSION_ID`	Trust an unpacked development extension by its Chrome extension ID.
`MCPX_PAIRING_TOKEN`	Supply a pairing token for recovery or controlled development setups.

Do not expose the selected port outside your computer.

Next step

Install and pair the browser in Connect the extension.