Lazaretto MCP server

lazaretto-mcp

Know what a package does before you install it.

An MCP server for Lazaretto: deterministic pre-install verification for npm packages, AI agent skills and MCP tools. The free lockfile check matches every exactly pinned dependency against OSV and OpenSSF malicious-package advisories with no account. A paid scan adds behavioral analysis with file-and-line evidence.

This package is a thin front end for the Lazaretto API. It ships no detection logic and does nothing but make HTTPS requests, so it is easy to audit.

Try it in one line, nothing installed

Check every exactly pinned dependency in your project against published malicious-package advisories. No account, no key, no install:

curl -s https://lazaretto.dev/check --data-binary @package-lock.json

Works with package-lock.json, npm-shrinkwrap.json, yarn.lock or pnpm-lock.yaml. We keep no copy of your lockfile.

Tools

check_lockfile (free, no API key)

Checks every exactly-pinned dependency in your lockfile against published malicious-package advisories. Reads package-lock.json, yarn.lock, or pnpm-lock.yaml from the working directory, so the agent never has to paste a lockfile through its context. One call covers the whole tree.

An empty malicious list is an all-clear only when unverified is also empty.

artifact? Exact-hash match against an indicator store refreshed daily.

• knownbadlookup: free, no key. Is a sha256 content hash a known-bad

attestation (compact JWS). Hand this tool one that another agent, a README, or a lockfile gave you: it confirms the signature is Lazaretto's, returns the attested claims, and flags contradicted if a once-clear subject is now known-bad, so a verdict can be trusted without re-scanning or re-paying. Still confirm the artifact you will run matches claims.sub.

• verifyattestation**: free, no key. A scan verdict ships with a signed

ClawHub skill, raw URL, or inline text) without running it and returns a deterministic verdict (malicious, flagged, clear, error) with evidence. A full scan needs prepaid credits (set an X-API-Key header). Buy them at https://lazaretto.dev/#pricing.

• scanartifact**: fetches a target (npm or PyPI package, GitHub repo,

of them, nothing can connect to it from outside, so there is no endpoint to check. Your client already read its tool list at startup though: paste that JSON and we analyze the same text with the same rules, contacting no server at all.

• checkmcptools: paid. For a server that runs over stdio, which is most

it. It asks the server to introduce itself and list its tools, then analyzes the text that server hands an agent: tool names, descriptions, parameter schemas, and its instructions. That text is documentation a model obeys, so it is an instruction channel the server controls. Catches tool poisoning (hidden directives to read ~/.ssh/id_rsa or an agent config file), parameters whose purpose is to carry secrets or your conversation out, and standing orders about another server's tools. Evidence names the exact tool. It calls only initialize and tools/list, never the server's own tools.

• scanmcpserver: paid. Point it at an MCP endpoint before you connect to

Reports are signals with evidence, not a warranty. clear means no known-bad match and no rule fired. It is not a statement about risk.

Use it (hosted, zero install)

The server is hosted at https://lazaretto.dev/mcp. Add it to any MCP client that supports remote (Streamable HTTP) servers. Nothing to install, no local process.

Shortened. The full README is on GitHub.