alfonsograziano/node-code-sandbox-mcp

Node.js server implementing the Model Context Protocol (MCP) for running arbitrary JavaScript in ephemeral Docker containers with on‑the‑fly npm dependency installation.
👉 Look at the official website
📦 Available on Docker Hub
Features
- Start and manage isolated Node.js sandbox containers
- Execute arbitrary shell commands inside containers
- Install specified npm dependencies per job
- Run ES module JavaScript snippets and capture stdout
- Tear down containers cleanly
- **Detached Mode:** Keep the container alive after script execution (e.g. for long-running servers)
> Note: Containers run with controlled CPU/memory limits.
Explore Cool Use Cases
If you want ideas for cool and powerful ways to use this library, check out the use cases section on the website
It contains a curated list of prompts, examples, and creative experiments you can try with the Node.js Sandbox MCP Server.
⚠️ Prerequisites
To use this MCP server, Docker must be installed and running on your machine.
**Tip:** Pre-pull any Docker images you'll need to avoid delays during first execution.
Example recommended images:
- node:lts-slim
- mcr.microsoft.com/playwright:v1.55.0-noble
- alfonsograziano/node-chartjs-canvas:latest
Getting started
In order to get started with this MCP server, first of all you need to connect it to a client (for example Claude Desktop).
Once it's running, you can test that it's fully working with a couple of test prompts:
- Validate that the tool can run:
This should run a console.log and in the tool response you should be able to see Hello World.
- Validate that you can install dependencies and save files
This should create a file in your mounted directory (for example the Desktop) called "qrcode.png"
Usage with Claude Desktop
Add this to your claude_desktop_config.json:
You can follow the Official Guide to install this MCP server
or with NPX:
> Note: Ensure your working directory points to the built server, and Docker is installed/running.
Docker
Run the server in a container (mount Docker socket if needed), and pass through your desired host output directory as an env var:
This bind-mounts your host folder into the container at the **same absolute path** and makes FILES_DIR available inside the MCP server.
Ephemeral usage – **no persistent storage**
Usage with VS Code
**Quick install** buttons (VS Code & Insiders):
Install js-sandbox-mcp (NPX) Install js-sandbox-mcp (Docker)
**Manual configuration**: Add to your VS Code settings.json or .vscode/mcp.json:
API
Tools
run_js_ephemeral
Run a one-off JS script in a brand-new disposable container.
**Inputs:**
- image (string, optional): Docker image to use (default: node:lts-slim).
- code (string, required): JavaScript source to execute.
- dependencies (array of { name, version }, optional): NPM packages and versions to install (default: []).
**Behavior:**
1. Creates a fresh container.
2. Writes your index.js and a minimal package.json.
3. Installs the specified dependencies.
4. Executes the script.
5. Tears down (removes) the container.
6. Returns the captured stdout.
7. If your code saves any files in the current directory, these files will be returned automatically.
- Images (e.g., PNG, JPEG) are returned as image content.
- Other files (e.g., .txt, .json) are returned as resource content.
- Note: the file saving feature is currently available only in the ephemeral tool.
> **Tip:** To get files back, simply save them during your script execution.
**Example Call:**
**Example to save a file:**
This will return the console output **and** the hello.txt file.