Browser JavaScript Evaluator MCP Server

@matdmiller

代码仓库

基本信息

分类

浏览器自动化

传输方式

stdio

作者

matdmiller

关于 Browser JavaScript Evaluator MCP Server

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.

Browser JavaScript Evaluator MCP Server 配置

使用下面的配置,将此服务器添加到你的 MCP 客户端。

{
  "mcpServers": {
    "mcp_py_sse_browser_control": {
      "command": "python",
      "args": [
        "web_server.py"
      ]
    }
  }
}

Browser JavaScript Evaluator MCP Server 工具

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当前收录暂时没有可展示的工具列表，不代表服务没有工具。请查阅项目文档了解支持的能力。

工具是从 README 中自动提取的。维护者可以在 ## Tools 标题下列出工具,即可填充这部分内容。

概览

What is Browser JavaScript Evaluator?

Browser JavaScript Evaluator is an MCP (Model Control Protocol) server that lets you execute arbitrary JavaScript code in a browser from Python. It uses a web server with SSE (Server-Sent Events) and a REST API to relay code to a connected browser and return results.

How to use Browser JavaScript Evaluator?

Add the server to your Claude Desktop configuration using uv pointing to the repository directory and the browser_server.py script. After launching Claude, open a browser to http://127.0.0.1:8000 to connect. The server provides two tools: execute_javascript (run any JavaScript) and add_numbers (add two numbers via browser execution).

Key features of Browser JavaScript Evaluator

Executes arbitrary JavaScript in a connected browser
Provides two MCP tools: execute_javascript and add_numbers
Uses SSE for real-time communication with the browser
Returns results synchronously via REST API
Web server and MCP server are split into separate components

Use cases of Browser JavaScript Evaluator

Perform browser‑based calculations from an MCP client (e.g., add_numbers)
Run custom JavaScript to manipulate or inspect a live browser page
Test and debug JavaScript code in a real browser environment
Automate browser interactions within an AI‑assisted workflow

常见问题

What does Browser JavaScript Evaluator do?

It allows you to execute JavaScript code in a browser from Python via MCP. A web server sends code to a connected browser using SSE, and the browser returns results.

How do I install and run it?

Add the server to your Claude config with the `uv` command pointing to the repository, then launch Claude. Open a browser at http://127.0.0.1:8000 to connect. Alternatively, run `python web_server.py` to start only the web server.

What MCP tools are available?

Two tools: `execute_javascript` (runs any JavaScript) and `add_numbers` (adds two numbers using JavaScript).

Is there a security warning?

Yes. The server can execute arbitrary JavaScript in your browser, which is potentially dangerous. Use at your own risk and be aware of the implications.

What are the dependencies or runtime requirements?

The server runs with Python and uses the `uv` package manager. A browser must be open and connected to the web server (default at port 8000) for code execution to work.

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