Certificate transparency search

Search public Certificate Transparency logs for every cert issued to a domain. Send POST /api/cert-transparency with the required field domain and pay $0.005 per call over x402 or MPP (there is no free tier). It returns a JSON object with domain, count, truncated, subdomains, certs and 2 more.

Two independent public CT search services are queried, the second only if the first is slow or fails, and `source` names the one that answered (their coverage windows differ). Returns the cert list plus a deduped subdomain set extracted from the SANs - the fastest way to enumerate subdomains for a security audit. No key required.

Category: Network & domains · Tags: security ssl tls certificates subdomain-discovery audit · Also found as: certificate-transparency-search certificate-transparency

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Parameters

Example request

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

Without payment this returns HTTP 402 Payment Required with the exact price for cert-transparency; any x402 v2 or MPP client pays it and retries.

Example response

{
  "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"
    }
  ],
  "source": "crt.sh",
  "queriedAt": "2026-06-19T22:00:00.000Z"
}

From an MCP client

catalog.call {
  "slug": "cert-transparency",
  "params": {
    "domain": "agent402.tools"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for cert-transparency; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• domain is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/cert-transparency returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

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();
client.setSpendControls?.(false); // keep your own spending ceiling in code
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

Certificate transparency search is one step in these 2 skill packs, each sold as a single call:

• 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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