Browser JavaScript Evaluator

Source

This is a reference design for a MCP server that hosts a web page that connects back to the server via sse and allows Claude to execute javascript on the page.

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Overview

This project provides a way to execute JavaScript code in a browser from Python using MCP (Model Control Protocol).

To use this project, add the MCP server to your Claude configuration and launch it. Then, open a browser and navigate to the provided local URL to connect to the web server.

Executes arbitrary JavaScript code in the browser from Python. - Provides a REST API for executing JavaScript. - Supports Server-Sent Events (SSE) for real-time communication.

Running JavaScript code snippets for testing and debugging.
Integrating JavaScript execution into Python applications.
Automating browser tasks using JavaScript.

Add to your AI client

Use these steps to connect Browser JavaScript Evaluator in Cursor, Claude, VS Code, and other MCP-compatible apps. The same JSON appears in the Use with menu above for one-click copy.

Cursor

Add this to your .cursor/mcp.json file in your project root, then restart Cursor.

.cursor/mcp.json

{
  "mcpServers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

Claude Desktop

Add this server entry to the mcpServers object in your Claude Desktop config, then restart the app.

~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows)

{
  "mcpServers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

Claude Code

Add this to your project's .mcp.json file. Claude Code will detect it automatically.

.mcp.json (project root)

{
  "mcpServers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

VS Code (Copilot)

Add this to your .vscode/mcp.json file. Requires the GitHub Copilot extension with MCP support enabled.

.vscode/mcp.json

{
  "servers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

Windsurf

Add this to your Windsurf MCP config file, then restart Windsurf.

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

Cline

Open Cline settings, navigate to MCP Servers, and add this server configuration.

Cline MCP Settings (via UI)

{
  "mcpServers": {
    "mcp-py-sse-browser-control-matdmiller": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-mcp-py-sse-browser-control-matdmiller"
      ]
    }
  }
}

FAQ

Is it safe to use this project?

This project can execute arbitrary JavaScript in your browser, which can be dangerous. Use at your own risk.

How do I run the web server independently?

You can run the web server independently by executing `python web_server.py` in your terminal.

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