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šŸ¢šŸš€ Node.js Sandbox MCP Server

@alfonsograziano

Repository

About šŸ¢šŸš€ Node.js Sandbox MCP Server

A Node.jsā€“based Model Context Protocol server that spins up disposable Docker containers to execute arbitrary JavaScript.

#node-js#javascript#typescript#docker

Config

Add this server to your MCP-compatible client using the configuration below.

{
  "mcpServers": {
    "js-sandbox": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-v",
        "/var/run/docker.sock:/var/run/docker.sock",
        "-v",
        "$HOME/Desktop/sandbox-output:/root",
        "-e",
        "FILES_DIR=$HOME/Desktop/sandbox-output",
        "alfonsograziano/node-code-sandbox-mcp"
      ]
    }
  }
}

Tools

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Overview

What is šŸ¢šŸš€ Node.js Sandbox MCP Server?

It is a Node.js server implementing the Model Context Protocol (MCP) for running arbitrary JavaScript in ephemeral Docker containers with onā€‘theā€‘fly npm dependency installation. It is for developers and AI agents who need an isolated, sandboxed JavaScript execution environment.

How to use šŸ¢šŸš€ Node.js Sandbox MCP Server?

Install and run via Docker or npx, then configure your MCP client (e.g., Claude Desktop, VS Code) with the provided JSON config. Pass environment variables like FILES_DIR, SANDBOX_MEMORY_LIMIT, and SANDBOX_CPU_LIMIT. Use tools such as run_js_ephemeral for oneā€‘off scripts or sandbox_initialize ā†’ run_js ā†’ sandbox_stop for sessionā€‘based workflows.

Key features of šŸ¢šŸš€ Node.js Sandbox MCP Server

  • Isolated Docker containers for each sandbox.
  • Execute shell commands inside running containers.
  • Install specified npm packages per job.
  • Run ES module JavaScript snippets and capture stdout.
  • Clean teardown of containers after use.
  • Detached mode for longā€‘running servers (background processes).

Use cases of šŸ¢šŸš€ Node.js Sandbox MCP Server

  • Quick oneā€‘off JavaScript experiments with automatic cleanup.
  • Run multiā€‘step scripts in a persistent sandbox environment.
  • Spin up temporary servers with exposed ports for testing.
  • Search npm packages and test them in isolation.
  • Generate files (e.g., QR codes, images) and retrieve them automatically.

FAQ from šŸ¢šŸš€ Node.js Sandbox MCP Server

What are the prerequisites?

Docker must be installed and running on your machine. Preā€‘pulling images like node:lts-slim is recommended to avoid delays.

How do I get files back from a script?

Save files during script execution in the containerā€™s working directory. Images (PNG, JPEG) are returned as image content; other files (e.g., .txt, .json) are returned as resource content. This feature is available only in the run_js_ephemeral tool.

What is detached mode?

Detached mode keeps the container alive after script execution, allowing longā€‘running services (e.g., servers) to stay active in the background. Use run_js with the listenOnPort parameter.

How can I limit container resources?

Set environment variables SANDBOX_MEMORY_LIMIT (e.g., 512m) and SANDBOX_CPU_LIMIT (e.g., 0.5) when launching the server.

Can I use custom Docker images?

Yes. The image parameter in tools like run_js_ephemeral and sandbox_initialize accepts any Docker image (default is node:lts-slim).

Frequently asked questions

What are the prerequisites?

Docker must be installed and running on your machine. Preā€‘pulling images like `node:lts-slim` is recommended to avoid delays.

How do I get files back from a script?

Save files during script execution in the containerā€™s working directory. Images (PNG, JPEG) are returned as image content; other files (e.g., .txt, .json) are returned as resource content. This feature is available only in the `run_js_ephemeral` tool.

What is detached mode?

Detached mode keeps the container alive after script execution, allowing longā€‘running services (e.g., servers) to stay active in the background. Use `run_js` with the `listenOnPort` parameter.

How can I limit container resources?

Set environment variables `SANDBOX_MEMORY_LIMIT` (e.g., `512m`) and `SANDBOX_CPU_LIMIT` (e.g., `0.5`) when launching the server.

Can I use custom Docker images?

Yes. The `image` parameter in tools like `run_js_ephemeral` and `sandbox_initialize` accepts any Docker image (default is `node:lts-slim`).

Comments

Basic information

Category

Reasoning

Transports

stdio

Author

alfonsograziano

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