# 402 Guard

> Small paid safety and live domain-intelligence checks for autonomous agents.

Canonical origin: https://x402.momentbolt.com
OpenAPI 3.1: https://x402.momentbolt.com/openapi.json
x402 discovery: https://x402.momentbolt.com/.well-known/x402
Agent skill contract: https://x402.momentbolt.com/skill.md
Health: https://x402.momentbolt.com/api/health
Free example input: https://x402.momentbolt.com/api/example
Paid payment-policy lint: POST https://x402.momentbolt.com/api/lint
Paid live domain audit: POST https://x402.momentbolt.com/api/domain-audit

The payment-policy lint costs $0.001 USDC using the x402 exact scheme on Base mainnet (`eip155:8453`). It returns a machine-readable report covering the x402 version, network, asset, recipient, amount, authorization timeout, EIP-712 domain, and duplicate payment options.

The live domain audit costs $0.002 USDC. Send `{"domain":"example.com"}` to receive current A, AAAA, MX, NS, TXT, CAA, and DMARC observations; SPF/DMARC/DNSSEC posture; an A–F grade; and actionable findings. DNS is resolved through Cloudflare's public DNS-over-HTTPS endpoint. Invalid input or upstream resolver failure is rejected before settlement.

Send an unauthenticated POST to either paid operation to receive a standards-compliant HTTP 402 response and `PAYMENT-REQUIRED` header. Use an x402-compatible client to sign the payment authorization, then retry with `PAYMENT-SIGNATURE`.

Neither operation asks for a caller private key or signs on the caller's behalf. Results are point-in-time technical checks; they do not establish ownership, counterparty legitimacy, deliverability, or financial safety.