SPF check

Fetch and validate a domain's SPF record (RFC 7208). Send POST /api/spf-check with the required field domain and pay $0.001 per call over x402 or MPP (there is no free tier). It returns a JSON object with domain, hasRecord, raw, mechanisms, lookupCount and 3 more.

Parses mechanisms (ip4/ip6/include/a/mx/all), counts DNS lookups against the famous 10-lookup limit, and flags the qualifier on `all` (-/fail, ~/softfail, ?/neutral). The first stop when an email is hitting the spam folder.

Category: Network & domains · Tags: spf email email-auth deliverability dns rfc7208

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Parameters

Example request

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

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

Example response

{
  "domain": "google.com",
  "hasRecord": true,
  "raw": "v=spf1 include:_spf.google.com ~all",
  "mechanisms": [
    {
      "type": "include",
      "qualifier": "pass",
      "value": "_spf.google.com"
    },
    {
      "type": "all",
      "qualifier": "softfail"
    }
  ],
  "lookupCount": 1,
  "all": "softfail",
  "valid": true,
  "warnings": []
}

From an MCP client

catalog.call {
  "slug": "spf-check",
  "params": {
    "domain": "google.com"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for spf-check; 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/spf-check 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/spf-check", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "domain": "google.com"
  }),
});

Part of these workflows

SPF check is one step in these 4 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.
• Email deliverability - Diagnose why a domain's email lands in spam: SPF posture, DMARC policy, DKIM key strength, MX targets, and a composite 0–100 score.
• Email security - Full email auth posture: SPF, DMARC, DKIM, and composite deliverability score in one call.
• Contact verification - Verify an email address is deliverable - syntax validation plus MX record check on the domain.

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