What is mcp-js?
mcp-js is a MCP server by r33drichards that javaScript sandbox that uses V8 isolation to run AI-generated code locally, with heap snapshotting for persistent sessions. It is listed under Developer tools and has 61 GitHub stars.
| Type | Mcp server |
|---|---|
| Author | r33drichards |
| Repository | r33drichards/mcp-js |
| Popularity | 61 GitHub stars |
| Category | Developer tools |
| Security | Review before installing (72/100) |
| Rank | #788 of 4,418 MCP servers; #193 in Developer tools |
| License | AGPL-3.0 |
| Last commit | 2026-10-18 |
| Runs | Locally |
| Language | Rust |
| Platforms | macOS, Linux |
Is mcp-js safe to install?
mcp-js scores 72/100 on the MCPMods security check: Review before installing. Things to review: can take actions such as send, write or deploy; executes code or shell commands. It passed 3 of 6 checks.
MCP server results come from listing signals: who publishes it, where your data goes and what it can do. The code itself is not scanned yet.
| Check | Result |
|---|---|
| Community-built server | Note |
| Runs on your machine only | Pass |
| No credentials mentioned | Pass |
| Can take actions such as send, write or deploy | Review |
| Executes code or shell commands | Review |
| Source on GitHub | Pass |
How do I install mcp-js?
- Find the launch command. The README says how the server starts (npx, uvx, docker or a remote URL) and which API keys it needs.
https://github.com/r33drichards/mcp-js
- Add it to Claude Code. Replace the part after -- with the command from the README. Remote servers use --transport http with a URL.
claude mcp add mcp-js -- <command from README> claude mcp add --transport http mcp-js <server-url>
- Check it connected. This lists your MCP servers and their status.
claude mcp list
Or ask Claude to set it up
Paste this into Claude Code and it installs mcp-js for you:
Add the "mcp-js" MCP server from https://github.com/r33drichards/mcp-js to Claude Code. Read its README for the launch command and any API keys I need, run claude mcp add, then check that it connects.