JavaScript Sandbox

Provides a secure JavaScript execution environment for running code snippets.

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js-sandbox MCP Server

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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

Installing via Smithery

To install JavaScript Sandbox Server for Claude Desktop automatically via Smithery:

npx -y @smithery/cli install @garc33/js-sandbox-mcp-server --client claude

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.

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