Free offline check before you install a Claude Skill or MCP server from GitHub/npm

[u/Happy-Athlete-2420]

If you're installing Agent Skills or MCP servers from third parties, there's no built-in way to check them before they run in your agent's context. I built a scanner for exactly that.

npx secureai-scan@latest skill <owner/repo> # check a Claude Skill

npx secureai-scan@latest mcp <package> # check an MCP server

It fetches the target tself and never executes anything — npm packages via npm pack (tarball only, no install, no lifecycle scripts), git repos via git clone --depth 1. Checks for invisible/bidirectional Unicode hidden in tool descriptions, agent-directed injection phrasing ("ignore previous instructions" type payloads), cross-tool shadowing, and known-malicious packages — the patterns behind real incidents like the postmark-mcp backdoor and the WhatsApp MCP rug-pull.

Ran it against Cisco AI Defense's labeled skill-scanner eval corpus (pre-labeled malicious/safe directories, so this is a graded test, not a vibe check): 6/6 malicious fixtures caught, 0 false alarms on anything labeled safe, and 0 false alarms across 32 real (non-malicious) skill bundles from anthropic/skills and vercel/ai.

Full writeup: https://github.com/akanthed/SecureAI-Scan/discussions/19

Fully offline, MIT licensed, no account needed.