js sandbox mcp server

Local 2025-09-01 00:06:49 0
Developer Tools @garc33/js-sandbox-mcp-server

Provides a secure, isolated JavaScript execution environment with configurable time and memory limits for safely running code from Claude.

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.

[
  {
    "description": "Execute JavaScript code in an isolated environment",
    "inputSchema": {
      "properties": {
        "code": {
          "description": "JavaScript code to execute",
          "type": "string"
        },
        "memory": {
          "description": "Memory limit in bytes",
          "maximum": 104857600,
          "minimum": 1048576,
          "type": "number"
        },
        "timeout": {
          "description": "Maximum execution time in milliseconds",
          "maximum": 30000,
          "minimum": 100,
          "type": "number"
        }
      },
      "required": [
        "code"
      ],
      "type": "object"
    },
    "name": "execute_js"
  }
]