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.

• known_bad_lookup: free, no key. Is a sha256 content hash a known-bad artifact? Exact-hash match against an indicator store refreshed daily.
• find_attestation: free, no key. Has anyone already attested this artifact? Give a package identity like chalk@5.6.1, an MCP server URL, or a sha256 content hash, and get the signed verdict if one exists, with its age, whether it was made under an older rules version, and contradicted if the subject is now known-bad. A miss means no attestation is on record for this subject. It is not a verdict either way.
• verify_attestation: free, no key. A scan verdict ships with a signed 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.
• scan_artifact: fetches a target (npm or PyPI package, GitHub repo, 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: the X-API-Key header on the hosted server, or LAZARETTO_API_KEY for the stdio package. Buy them at https://lazaretto.dev/buy.
• scan_lockfile_deep: paid, one credit per package that returns a verdict. The behavioral counterpart to check_lockfile: reads the code of every exactly pinned dependency, up to 25 per call, instead of only matching names and versions. Trust complete_coverage: false means something was capped, errored or only partly read, so the run is not a clean bill of health for the tree. Calling again with the same lockfile rescans, and bills again, the same first packages. The result lists every package it left in not_scanned.packages, as name@version strings. To continue a run, pass those as packages instead of the lockfile:
  • Hosted server (https://lazaretto.dev/mcp): pass not_scanned.packages back as packages, the whole list. It scans the first 25 and lists the rest in not_scanned.packages again.
  • stdio package: packages takes up to 25 per call, so work through not_scanned.packages 25 at a time. The tool adds next_call to the result, and next_call.packages holds the first 25 of that list.
• check_mcp_tools: paid. For a server that runs over stdio, which is most 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.
• scan_mcp_server: paid. Point it at an MCP endpoint before you connect to 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.

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.

{
  "mcpServers": {
    "lazaretto": {
      "url": "https://lazaretto.dev/mcp",
      "headers": {
        "X-API-Key": "your-prepaid-key (optional; the free tools need no key)"
      }
    }
  }
}

check_lockfile, known_bad_lookup, find_attestation and verify_attestation work with no key. scan_artifact, scan_lockfile_deep, scan_mcp_server and check_mcp_tools need credits: buy a pack at https://lazaretto.dev/buy (an agent with a wallet can also buy credits itself over x402 at POST https://lazaretto.dev/v1/credits/topup).

Self-host the stdio server (optional)

If you would rather run it locally over stdio instead of the hosted URL, the npm package is lazaretto-mcp:

{
  "mcpServers": {
    "lazaretto": {
      "command": "npx",
      "args": ["-y", "lazaretto-mcp"],
      "env": {
        "LAZARETTO_API_KEY": "your-prepaid-key (optional; the free tools need no key)"
      }
    }
  }
}

Or from a clone:

git clone https://github.com/jamesdfinance-dev/lazaretto-mcp
cd lazaretto-mcp && npm ci
read -rs LAZARETTO_API_KEY && export LAZARETTO_API_KEY
node index.mjs

The stdio package pays only with prepaid credits on LAZARETTO_API_KEY. It has no x402 client of its own, so a paywall result carries no x402 payment challenge: per-call x402 payment must be made by the agent's own HTTP client against https://lazaretto.dev/v1/scan, not through this package. LAZARETTO_BASE_URL overrides the API host (default https://lazaretto.dev).

License

MIT. The Lazaretto service and its detection engine are separate and proprietary.