Certificate transparency search

Search public Certificate Transparency logs (via crt.sh) for every cert issued to a domain. Returns the cert list plus a deduped subdomain set extracted from the SANs - the fastest way to enumerate subdomains for a security audit. Free upstream, no key required.

Input

Example output

{
  "domain": "agent402.tools",
  "count": 2,
  "truncated": false,
  "subdomains": [
    "agent402.tools"
  ],
  "certs": [
    {
      "id": 1234567890,
      "serial": "0a:1b:2c",
      "issuer": "C=US, O=Let's Encrypt, CN=E5",
      "commonName": "agent402.tools",
      "sans": [
        "agent402.tools"
      ],
      "notBefore": "2026-01-15T00:00:00",
      "notAfter": "2027-02-14T23:59:59"
    }
  ],
  "queriedAt": "2026-06-19T22:00:00.000Z"
}

Try it - see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/cert-transparency \
  -H "Content-Type: application/json" \
  -d '{"domain":"agent402.tools"}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/cert-transparency", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "domain": "agent402.tools"
  }),
});

Part of these workflows

This tool is one step in 2 curated multi-tool workflows - agents can fetch the whole sequence as an MCP prompt or call https://agent402.tools/api/skill-packs/{slug}/prompt.

• Security audit - Enumerate a domain's external attack surface in one workflow: certs, DNS posture, email auth, HTTP security headers, and tech stack.
• Fraud signals - Is this domain trustworthy, or is it a phishing site / typosquat / scam? Pull the reputation signals an analyst checks before clicking anything: domain age, cert issuance history, hosting reputation, DNS topology, tech-stack fingerprint, and page-content red flags. Different from a security audit - this is about whether the domain is what it claims to be.

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