Domain authentication check — free API, no key

Check whether anyone can send email as a domain.

curl "https://guild.tradeuniquecapital.com/api/check?domain=example.com"

No signup, no API key, no account. 20 calls per caller per hour.

It runs the same engine as the paid audit over one domain and returns what it actually found — not a teaser with the findings removed.

Every check gets a page you can send to someone

{
  "domain": "stripe.com",
  "grade": "A",
  "report_url": "https://guild.tradeuniquecapital.com/r/bad8482e9e93"
}

A permanent, shareable page with the verdict, the records found, and what to change — the thing you forward to whoever runs the DNS. Kept 90 days.

A correctly configured domain gets a page saying so, with nothing to buy.

Related MCP server: intodns-mcp

What it checks

• SPF, including the RFC 7208 ten-lookup limit that silently breaks it

• DKIM selectors

• DMARC — and whether it enforces or only monitors, which is the difference between protection and a report nobody reads

• Cross-domain DMARC reporting authorisation (RFC 7489 §7.1) — the external rua authorisation record almost nobody publishes

• MX and null-MX (RFC 7505)

The one rule it follows

A failed lookup is never reported as a finding.

If a DNS query times out, the response says the check was incomplete. It does not say "no SPF record". Those mean different things, and only one of them is a problem with the domain — telling somebody they are unprotected when they may be fine is the worst thing a checker can do.

{
  "domain": "example.com",
  "grade": "B",
  "checks_completed": 3,
  "checks_total": 4,
  "complete": false,        // ← treat as unknown, not as a fault
  "findings": { "...": "..." }
}

Install

pip install httpx     # or use urllib; the client has no hard dependency

Then copy agpc_domain_check/client.py, or:

from agpc_domain_check import check

result = check("example.com")
print(result["grade"], result["findings"]["dmarc"])

JavaScript is in examples/check.js — it is twenty lines and has no dependencies.

MCP server — plug it into any agent

The API is also an MCP server, so Claude (or anything MCP-capable) can call it as a native tool:

https://guild.tradeuniquecapital.com/mcp

Streamable HTTP, stateless, no auth, no key. Three tools:

Claude Code: claude mcp add --transport http agpc https://guild.tradeuniquecapital.com/mcp

Machine-readable

Point any agent framework at the OpenAPI document and it can call this unattended.

Earn from it

If you send someone who buys the full audit, you take 25% of the settled amount — EUR 37.25 per audit.

curl -X POST https://guild.tradeuniquecapital.com/partners/terms \
  -H 'Content-Type: application/json' \
  -d '{"agent_id":"your-agent","code":"YOURCODE","rate":0.25}'

Then send people to https://guild.tradeuniquecapital.com/order?ref=YOURCODE.

• Up to 25% is accepted immediately. Above that is reviewed, not refused. Above 40% is refused — past that the referral costs more than the work earns.

• Paid when the order settles — the money is in the account, not merely promised.

• Reversed if the order is refunded. You are not paid for our bad debt.

Not paid for: traffic or leads that never pay, refunded orders, and anything obtained by deception, spam, unlawful scraping, or access to systems you are not authorised to use.

What the paid audit adds

Up to five domains in one order, DKIM probed across 34 known provider selectors, prioritised remediation with the exact records to publish, and a written report you can hand to whoever runs the DNS. EUR 149, one-time.

Who runs this

Marko Latinović, a natural person resident in Serbia, in a personal capacity. Not a company. There are no customer testimonials, because there are no customers yet, and inventing them would be the first thing worth distrusting about a security service.

Contact: markol@tradeuniquecapital.com

Licence

MIT for the client code in this repository. The API is free to call within the stated rate limit.