js-sandbox MCP Server

js-sandbox MCP Server

A Model Context Protocol server that provides a secure JavaScript execution environment.

Features

Tools

• execute_js - Executes JavaScript code in an isolated environment
  • Parameters:
    • code (required): JavaScript code to execute
    • timeout (optional): Maximum execution time in milliseconds (100-30000ms)
    • memory (optional): Memory limit in bytes (1MB-100MB)
  • Returns the result of code execution

Security

• Isolated code execution in a controlled environment
• Configurable execution time and memory limits
• Protection against malicious code

Development

Install dependencies:

npm install

Build the server:

npm run build

Development mode with auto-rebuild:

npm run watch

Installation

To use with Claude Desktop, add the server configuration:

MacOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "js-sandbox": {
      "command": "/path/to/js-sandbox/build/index.js"
    }
  }
}

Debugging

Since MCP servers communicate over stdio, debugging can be challenging. We recommend using MCP Inspector, which is available as:

npm run inspector

The Inspector will provide a URL to access debugging tools in your browser.