NEL VEIL MCP — free domain security checks for AI agents

Ask your agent "can someone spoof email from example.com?" and get a real answer in about ten seconds.

NEL VEIL MCP gives any MCP-compatible agent seven tools for checking a domain's public security posture: email spoofing (DMARC/SPF/DKIM), TLS weaknesses, HTTP security headers, publicly exposed files, subdomain-takeover risk, a combined scan, and retrieval of an earlier scan.

Free. No API key. No signup.

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Install

Claude Code — one command:

claude mcp add nel-veil -- npx -y nel-veil-mcp

Any MCP client — add this to your config file:

{
  "mcpServers": {
    "nel-veil": {
      "command": "npx",
      "args": ["-y", "nel-veil-mcp"]
    }
  }
}

Run it directly, to check it works:

npx -y nel-veil-mcp

It prints a ready line to stderr — something like nel-veil-mcp 0.1.5 ready — 7 tools, free passive tier. — and then waits for JSON-RPC on stdin. That is correct: it is a stdio server, not a CLI, and stdout carries the protocol, so nothing else is ever written there.

Requires Node 18 or newer.

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30 seconds: is your domain spoofable?

After installing, ask your agent:

Check if example.com can be email-spoofed.

It calls check_email_spoofing. Real output for example.com at the time of writing:

Check if a domain can be email-spoofed — example.com
Score: 100/100 (done)

2 findings:
  [LOW] DMARC has no reporting address (rua/ruf), you have no visibility into spoofing
  [LOW] DKIM key may be 1024-bit (weak), 2048-bit recommended

Free check, built from public information. No port scanning and no exploit testing —
though some checks (TLS via Qualys SSL Labs, admin-panel reachability) do more than
passive reading; see nelprofessional.com/mcp. Active scanning requires verified domain
ownership and runs only at nelprofessional.com.
More: https://www.nelprofessional.com/mcp

That domain is in good shape. The finding people are most often surprised by is a DMARC policy of p=none — it looks configured, monitors everything, and blocks nothing.

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Tools

Tool	Answers
check_email_spoofing	Can someone send email that appears to come from this domain? (DMARC/SPF/DKIM)
check_tls	Does this domain's TLS have known weaknesses? (Qualys SSL Labs grade — see the note below)
check_security_headers	Does this site send the headers that protect visitors in the browser?
check_exposed_files	Is this domain publicly serving files it should not be?
check_subdomain_takeover	Are there DNS records pointing at services someone else could claim?
scan_domain	All of the above at once, with a per-module score.
get_scan_report	Retrieve a scan already run at nelprofessional.com, by its scn_… id.

Each returns a 0–100 score plus specific findings you can act on.

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What this sends — stated plainly

Being precise here matters more than sounding safe, because this is the paragraph you rely on when deciding whether you may point a tool at someone else's domain.

No tool here does port scanning or exploit testing. Those are genuinely intrusive, they need the domain owner's permission, and they are deliberately not exposed over MCP at all.

But "passive" is not the same as "invisible", and two tools do more than read public records:

• check_tls is not passive. It queries Qualys SSL Labs, which performs its own active TLS assessment of the target from Qualys's infrastructure (reusing a recent cached result when Qualys has one). NEL sends no probe itself, but running this does cause the target to be actively tested by a third party. It returns the SSL Labs grade and known problems — Heartbleed, POODLE, RC4, deprecated protocols, weak forward secrecy, certificate chain issues. It does not report certificate expiry, issuer, or hostname validity.
• check_subdomain_takeover is not DNS-only. It resolves a small fixed list of common subdomain names and makes one HTTPS request to any that point at a known cloud host. It never claims or modifies anything.
• check_exposed_files requests a small fixed list of well-known paths (.env, .git/config and similar). It never brute-forces or fuzzes — the list does not grow or adapt — but these are paths a crawler would not request, so they are recognisable in a target's logs as a security check.
• scan_domain runs all of the above, and additionally checks whether common admin panels (/phpmyadmin/, /manager/html) are publicly reachable.

Everything above is information the domain publishes. None of it attacks anything. But it is more than ordinary crawling, so prefer running it against a domain you own or are authorised to assess.

Active scanning — port exposure, API probing, proof-of-concept checks — lives at nelprofessional.com, behind DNS-TXT proof that you control the domain. That is the right place for it, because a human proves ownership once and NEL can stand behind the result.

Rate limits. Ten single checks and three full scans per minute, per IP address. If you hit it, wait a minute.

Privacy. This package sends no API key, no email address, and no account identifier. Each request carries the domain you asked about and a nel-veil-mcp user-agent. Note that, like any HTTP service, NEL sees the IP the request came from — it is what the rate limit is keyed on.

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Configuration

Variable	Default	Purpose
NEL_API_URL	https://api.nelprofessional.com	Point at a self-hosted NEL backend. Only needed for local development.

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Development

These steps need the git repository, not the published npm package — the tarball ships only dist/, so src/ and scripts/ are not in it.

git clone https://github.com/NELPROINC/nel-veil-mcp.git
cd nel-veil-mcp
npm install
npm run build
node scripts/mcp-smoke.mjs example.com

scripts/mcp-smoke.mjs launches the built server exactly as npx would, performs the MCP handshake, lists the tools and calls one for real — so it catches transport and schema problems a unit test would not.

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About NEL VEIL

NEL VEIL is the security scanner behind NEL Professional, a marketplace connecting organisations with verified cybersecurity professionals. The same modules that power this MCP server power the scans on the site.

Full documentation: nelprofessional.com/mcp

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License

MIT — see LICENSE.