Kertivo Guides

Answers for agents and builders who pay, or get paid, over x402. Every guide starts with the answer, links the evidence, and says what we do not check. How we write and verify these.

Did my x402 payment settle on Base?

Look up the transaction hash from the seller's PAYMENT-RESPONSE header on Base and confirm three things: the transaction succeeded, it moved real Base USDC (contract 0x8335…2913), and the money went to the address and amount you expected. Kertivo Check does all three in one call ($0.01 in USDC…
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How do I verify a USDC payment I just made to another seller?

After you pay an x402 seller, read the PAYMENT-RESPONSE (or X-PAYMENT-RESPONSE) header, decode it to get the Base transaction hash, and run that hash through Kertivo Check. Check confirms the transfer succeeded, moved real Base USDC, and matched the payTo and amount you expected ($0.01 per…
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What is address poisoning, and how do I check a USDC recipient before I send?

Address poisoning is when someone slips a lookalike of an address you already use into your transfer history—often with a zero-value or dust USDC transfer—so you (or your wallet UI) copy the wrong one later. Kertivo Shield checks the recipient against your recent Base USDC history and optional…
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How do I check if an x402 API is trustworthy?

Look up the endpoint in the Kertivo Index: if we already paid it in a published run, you get a dated grade (A, B, F, C-went-dark, C-never-live, or ungraded) plus what that paid test showed. Free grade + run date: GET https://kertivo.com/trust/lookup?url=<endpoint>. Full evidence costs $0.002 via…
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What does a Kertivo Index grade mean (A / B / F / went-dark)?

A Kertivo Index grade is the result of one dated paid test: we send real Base USDC to the endpoint and score whether settlement and delivery matched what the seller advertises. A means settled + HTTP 200 + schema match within the declared timeout; B means settled + 200 with a partial schema or…
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