Trust & Safety · How to evaluate a seller

How do I check a seller before my agent pays it?

With public evidence, one question at a time. Every check on this page can be run today, for free, with a browser — no account, no tools to buy. Each check is a question, and each names the public evidence that answers it.

Where do these checks work best?

They work best where payments are public. As of 2026-09-02, x402 payments settle in USDC on the Base network, so a seller’s payment history sits on-chain — on a public ledger anyone can inspect. Card-rail purchases leave no public ledger; there, the rail’s built-in dispute process is the backstop instead.

One limit to carry through the whole page: public payment history proves that money moved. It cannot prove the work was good — that is the verification hole. These checks lower the odds of paying a fake. They do not grade anyone’s work.

Check 1: Does the seller publish a payment address?

An on-chain seller has a receiving address, and a checkable seller does not hide it. Look in the seller’s catalog listing and its documentation. If your agent has already paid once, the settled transaction names the recipient — the address is on your own receipt.

• What answers it: the seller’s own listing or documentation; any past settled payment to it.
• Good sign: one stable address, published where buyers can find it.
• Warning pattern: no findable address. Then no other check on this page can run — and every claim the seller makes stays unchecked.

Check 2: Does on-chain history show buyers who come back?

A working service accumulates history that is hard to fake well: many distinct buyers, arriving over months, paying amounts that match the published price — and returning. Paste the seller’s address into a public Base block explorer, such as BaseScan, and read the incoming transfers.

• What answers it: the public ledger — incoming USDC transfers to the seller’s address, viewable in any Base block explorer.
• Good signs: distinct payers spread over time; repeat payments; amounts that match the price list.
• Warning patterns: most volume arriving from a handful of payers (concentration risk); money circling back out to the payers (wash trading); swarms of near-zero payments (dust). Each pattern is described in full on the failure-modes page.

Reading a ledger takes patience, and that is fine. The point is that you can — and that no seller can stop you.

Check 3: Is the pricing sane?

A price has to make sense twice: against comparable services, and against itself. First compare the seller’s published price with the published prices of comparable services. Then confirm that the price its service actually quotes matches its listing — in the x402 flow, the service names its price in the 402 answer it returns when asked.

OTTO, our example AI agent, buys text extraction at $0.01 per page. Its operator runs the self-consistency check in one request: ask the service for its price, and confirm the quote matches the listed $0.01. A seller whose quote and listing disagree has failed a check before any work is judged.

• What answers it: the seller’s published price list; the price its service quotes when asked; comparable sellers’ published prices.
• Good sign: quote and listing agree, and the price sits near comparable services.
• Warning patterns: quote and listing disagree; a price far outside comparable services, in either direction, with no stated reason.

Check 4: Are the seller’s claims sourced?

A claim you cannot check should carry no weight — not treated as false, just as unchecked. Sellers claim request volumes, revenue, uptime, customer counts. For each claim, ask one question: what public record backs this?

• What answers it: the claim itself, and whatever public record it points to.
• Good sign: claims that point at checkable records — for example, an address whose on-chain history matches the claimed activity. That is what this site calls recomputable.
• Warning patterns: self-reported figures with no public trail; screenshots offered as proof. Screenshots are exactly what disputes collapse to.

After the checks pass, then what?

Spend a little first. Before granting a standing mandate, make one small purchase and read what comes back. The receipt cannot grade the work — but you can.

Then cap it. Keep a spending cap on the agent no matter how good the checks looked. The checks lower the risk; the cap bounds it.

This checklist is manual today. The same signals — buyer spread, dust filtering, price sanity — are what this site’s published numbers will be built from. The method is public in the methodology.

Where are the primary sources?

• Read the x402 specification — the payment flow, including the 402 answer that names price, network, and token.
• Read x402.org — the protocol’s own site: stablecoin payments as the primary use case.
• Use BaseScan — a public block explorer for the Base network, where check 2 runs.