javascript-sandbox-mcp

# JavaScript Sandbox MCP Server A Model Context Protocol (MCP) server that executes JavaScript code securely in a sandboxed environment using [SES (Secure ECMAScript)](https://github.com/endojs/endo/tree/master/packages/ses). https://github.com/user-attachments/assets/654f71e7-fb88-41ca-a6d0-634cc07fe426 ## Features ### Tools - `run_javascript` - Execute arbitrary JavaScript code in a secure SES compartment - Accepts a string of JavaScript code - Returns the result and all console logs as JSON-formatted text ## Development Install dependencies: ```bash npm install ``` Build the server: ```bash npm run build ``` For development with auto-rebuild: ```bash npm run watch ``` ## Usage You can run the server directly: ```bash npm start ``` Or use the built binary: ```bash node build/index.js ``` ## Installation To use with Claude Desktop, add the server config: On MacOS: `~/Library/Application Support/Claude/claude_desktop_config.json` On Windows: `%APPDATA%/Claude/claude_desktop_config.json` ```json { "mcpServers": { "run-javascript-sandbox": { "command": "npx", "args": ["-y", "javascript-sandbox-mcp"] } } } ``` ### Debugging Since MCP servers communicate over stdio, debugging can be challenging. We recommend using the [MCP Inspector](https://github.com/modelcontextprotocol/inspector): ```bash npm run inspector ``` The Inspector will provide a URL to access debugging tools in your browser. --- **Security Note:** This server uses SES to sandbox code execution, but running untrusted code always carries risk. Use with caution and only in trusted environments.