Frequently asked questions

x402 is a machine-payment protocol built on the HTTP 402 "Payment Required" status code. An API returns 402 with payment terms, the caller (often an AI agent) pays on-chain, and retries the request with proof of payment attached. There's no account, no invoice, and no human approving the transaction — which is what makes it fast for agent-to-agent commerce, and also what makes it blind: the provider sees the payment only after it has already settled.

ERC-8004 is an Ethereum standard for on-chain agent identity and reputation. It gives an autonomous agent a registered identity (an agent ID) that can accumulate reputation signals over time, separate from any single wallet address. vet402 reads ERC-8004 identity and reputation data — alongside raw wallet activity — as one of the signal groups behind a trust score.

Given an ERC-8004 agent ID or a wallet address, vet402 returns a trust score (0-100), a recommendation (ALLOW / WARN / BLOCK), and the underlying signal breakdown: identity, reputation, wallet history, x402 payment history, and sybil-risk indicators. It's meant to be checked in the request path — before you accept a payment or complete a transaction — not reviewed after the fact.

No. Scores are informational signals derived from public on-chain data and ERC-8004 records. They do not constitute a guarantee, a credit assessment, KYC, or legal certification of any counterparty. Every API response includes this disclaimer directly in the payload so it travels with the data.

Primarily x402 API providers and platforms that accept payment from agents they've never seen before, and need a signal before completing the request. It's equally useful the other direction: an agent that is about to pay an unfamiliar wallet can check that payee's score first. The API doesn't assume which side of the transaction is calling it.

Not as a dedicated category yet. x402 and ERC-8004 only shipped in 2025, so "score a payee before an agent pays them, specifically for x402 machine payments" isn't a shelf with incumbents on it the way wallet AML screening or credit scoring is. General crypto wallet-risk tools score addresses for sanctions and fraud exposure, not for x402 payment trust; general agent-identity and reputation projects don't yet gate a payment decision in the request path. We checked this directly rather than assuming it: running vet402's own query through independent AI answer engines returned no vendor at all for "payee trust API for x402" — not vet402, not a competitor. That cuts both ways. There's no incumbent to unseat, but it also means the need is still being proven out as x402 transaction volume grows, not a solved problem we're improving on.

No. vet402 is a read-only scoring and attestation API — it never holds, moves, or has signing authority over funds. The SDK's SpendGuard module (non-custodial) helps an agent apply spend policy locally before it pays; vet402 itself only returns scores and records settlement attestations after a payment has already happened on-chain.

Base. Wallet and ERC-8004 signals are read from Base mainnet. Support for additional chains isn't ruled out, but nothing beyond Base is live today — check the API reference for the current signal set.

The free tier covers 1,000 lookups a month, enough to wire a score check into an x402 flow and see real results before committing to anything. Paid plans add higher volume and score-history access. See the pricing section on the homepage for current tiers.

Score by agent ID (GET /api/v1/agents/:agentId/score) or by wallet address (GET /api/v1/wallets/:address/score — the primary path for x402 middleware), batch up to 25 at once, or attest an x402 settlement after verification. Full request/response shapes, error codes, and an OpenAPI schema are on the API reference page.