Lazaretto

Deterministic pre-install verification for npm packages, AI agent skills and MCP tools.

CommunityOnlineNo sign-inGlobalFreeRead-only

What it can do

  • Known Bad Lookup: Check a SHA-256 against Lazaretto's known-bad indicator set (refreshed daily from abuse.ch). Free and anonymous. A miss only means this exact hash is not in the indicator set; it is
  • Check Lockfile: Check every EXACTLY-PINNED dependency in a lockfile against published malicious-package advisories (OSV/OpenSSF). Free, anonymous, one call for the whole tree. Accepts the contents of
  • Scan Artifact: Deterministically analyze a package, repo, skill, or file for malicious behavior (credential theft, data exfiltration, obfuscation, prompt injection aimed at the agent, install scripts)

What data it sees

Do you need an account

No: the server works without sign-in

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. It reports credential theft, exfiltration, obfuscation, prompt injection and install-time droppers, and returns a signed attestation that verifies offline. No LLM runs in the scan path, so the same input yields the same verdict. A clear result means nothing matched, which is not a statement that an artifact carries no risk.

How to connect

How to connect Lazaretto to Claude

The server address to paste into Claude settings:

https://lazaretto--jamesdfinance.run.tools

  1. Open Claude (claude.ai or the desktop app).
  2. Go to Settings → Connectors.
  3. Click Add custom connector.
  4. Paste the server address copied below into Remote MCP server URL and click Add.
  5. In a chat, click + → Connectors and switch the new connector on.

Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

Authorization

After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

How to connect Lazaretto to ChatGPT

The server address to paste into ChatGPT settings:

https://lazaretto--jamesdfinance.run.tools

  1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
  2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
  3. Open Settings → Connectors and click Create.
  4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
  5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
  6. In a new chat open + → Apps/Connectors and enable the connector.

OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

Authorization

On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

How to connect Lazaretto to Cursor

The server address to paste into Cursor settings:

https://lazaretto--jamesdfinance.run.tools

Fastest: click Open in Cursor below and confirm the prompt.

Manually:

  1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
  2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
  3. Save the file. The server appears in the MCP list; authorize it there if asked.

Authorization

If the service needs sign-in, an authorize button appears next to the server in the MCP list.

Server tool list (5)

Raw names from tools/list. Only developers need these.

known_bad_lookupCheck a SHA-256 against Lazaretto's known-bad indicator set (refreshed daily from abuse.ch). Free and anonymous. A miss only means this exact hash is not in the indicator set; it is not a clean verdict on the artifact.
check_lockfileCheck every EXACTLY-PINNED dependency in a lockfile against published malicious-package advisories (OSV/OpenSSF). Free, anonymous, one call for the whole tree. Accepts the contents of a package-lock.json, yarn.lock, or pnpm-lock.yaml. Only exact versions can be answered: a range like ^5.0.0 has no definitive answer because a compromised release usually sits between clean ones. Fail-closed: anything that could not be checked is returned in `unverified`, so an empty `malicious` list is an all-clear only when `unverified` is empty too.
scan_artifactDeterministically analyze a package, repo, skill, or file for malicious behavior (credential theft, data exfiltration, obfuscation, prompt injection aimed at the agent, install scripts) and return a verdict (malicious, flagged, clear, error) with the exact evidence and a hash of what was scanned. Metered: present an X-API-Key holding credits. If you hold a wallet instead of an account, pay per call over x402 at POST https://lazaretto.dev/v1/scan ($0.03 USDC on Base, no signup). A free key with a daily allowance is available at POST https://lazaretto.dev/v1/trial. For checks that are always free, use check_lockfile or known_bad_lookup.
scan_lockfile_deepBehaviorally scan EVERY exactly-pinned dependency in a lockfile, not just their identities: reads the code of each package and reports credential theft, exfiltration, obfuscation, prompt injection and install-time droppers with file-and-line evidence. This is the paid counterpart to check_lockfile, which only matches names and versions against advisories. Metered: one credit per package that returns a verdict, nothing for one that errors. Capped at 25 packages per call. Use it before installing a tree you have not vetted.
verify_attestationVerify a Lazaretto scan attestation that another agent (or a README, or a lockfile) handed you, WITHOUT re-scanning or paying. Free and anonymous. Returns whether the signature is valid and Lazaretto's, the attested claims (verdict, risk, and the subject the verdict is about), and a `contradicted` flag if a previously-clear subject is now known-bad. You MUST still confirm the artifact you are about to run matches `claims.sub` (its sha256, or its package identity).