KertivoWhat is x402, and why do bot-to-bot payments need a trust layer?
x402 is an open HTTP payment protocol that turns the long-reserved 402 Payment Required status into a real pay-per-request handshake: the server quotes a price, the client retries with a signed payment, and settlement can happen on-chain (commonly USDC). Bots can pay APIs without checkout pages — but settlement and delivery can disagree, lookalike addresses exist, and a seller's marketing is not a receipt. Kertivo is a trust layer for those payments: verify settlement, check recipients, grade paid tools from real USDC tests, and publish buyer claims. Grades are earned, never bought.
Who this is for
- Builders meeting x402 for the first time who want the protocol shape before the product pitch.
- Agents that already pay x402 routes and need language for why an independent check exists.
- Humans evaluating whether "agent commerce" volume equals trustworthy counterparties (spoiler: it does not).
How x402 works (protocol)
Per the open docs (HTTP 402 — x402, How x402 works — Coinbase Developer docs):
- Client requests a resource.
- Server answers HTTP 402 with payment requirements (price, asset, network, payee) — in v2 often via a
PAYMENT-REQUIREDheader. - Client signs a payment and retries with proof (v2:
PAYMENT-SIGNATURE). - Server verifies / settles (often via a facilitator) and returns the resource with a
PAYMENT-RESPONSE(success, transaction hash, network, payer).
Design goals called out in those docs: machine-to-machine payments, pay-per-use APIs, micropayments without account signup. The handshake is transport-oriented; sellers choose networks and assets. USDC on Base is what Kertivo's paid routes accept today (eip155:8453, payTo published in /llms.txt).
Nothing in the protocol forces the seller to deliver useful data after money moves. Nothing on-chain proves the HTTP body was correct. That gap is why a trust layer exists.
Why bots need more than "it returned 200"
When software pays software:
- Settlement ≠ delivery. A payment can confirm on Base while the seller returns an error, times out, or never responds. Keep the tx hash; verify with Check (
POST /check, freePOST /demo). - Addresses can look alike. Dust or zero-value transfers to lookalike recipients ("address poisoning") train wallets to copy the wrong
to. Kertivo Shield checks the recipient before you send (see Guide #3; free fixture:POST https://kertivo.com/demo/address). - Marketing ≠ a paid test. An Index grade is one dated Kertivo payment + delivery check, not an endorsement of honesty or data quality. See Guide #5.
- Disputes need public evidence. Free Claims prove payment on-chain; delivery remains the buyer's report. Kertivo does not custody funds or arbitrate.
Kertivo's brand line (live on the site and /llms.txt): Kertivo exists so machines can trust who they pay. One-liner: Kertivo is the trust layer for bot-to-bot payments. Grades are earned, never bought.
Ecosystem scale (third-party, not a Kertivo metric)
TRM Labs' public analysis Who's Actually Paying? Measuring AI Agent Payments Onchain (Sep 9, 2026) measured settlements through known x402 facilitators across Base, Solana, and Polygon since May 2025: roughly USD 52.7M across ~198.9M settlement transactions. After removing self-payment, bulk flows from one or two payers, and sellers with fewer than ten distinct buyers, about half of that volume falls away (USD 25.62M of screened commerce remains), and their two tests put the share that appears agentic at only 0.6%–7.5% of it. They describe the volume those agents move as small, roughly USD 5,000–11,000 a month. On a test with no asset constraint, 99.6% of value (USD 52.47M of 52.68M) settled in USDC.
Read that as: the rail is real and observable, but headline volume is not "all agents buying services," and counterparty reputation still has to be checked per payment. Kertivo does not publish competing market-size estimates.
What Kertivo covers today
| Need | Product | Price and notes |
|---|---|---|
| Did this USDC payment settle? | Check (/check, /check/deep) | $0.01 / $0.05 (deep also reads the payer's funding history before the payment). Free: POST /demo rehearses your /check body on a fixed demo tx |
| Is this recipient a poisoning lookalike? | Shield (/address/check, /address/check/full) | $0.001 recent window / $0.005 history from one index read (up to the sender's 500 most recent Base USDC transfers, usually the whole history; coverage.historyComplete says when it is). Free fixture: POST /demo/address |
| Did this endpoint earn a grade in a paid Index run? | Index + /trust/lookup | Free grade-only GET /trust/lookup?url=; $0.002 POST adds evidence |
| Paid but got nothing useful? | Claims (POST /claim) | Free; evidence only |
| Show a grade on a README | Badge (GET /badge/<url-encoded-endpoint>) | Free; earned, never sold |
| Filter a JSON or NDJSON event log | Logs (POST https://logs.kertivo.com/filter) | $0.005 per call |
Machine entry points: /llms.txt, /openapi.json, /examples.
Try it
- Read the live scorecard: https://kertivo.com/trust-index.
- Free settlement demo:
curl -sS -X POST https://kertivo.com/demo(send your real/checkbody to rehearse your field mapping; it always answers on the fixed demo transaction). - Free grade lookup:
curl -sS 'https://kertivo.com/trust/lookup?url=https://api.onesource.io/api/chain/erc20-balance'.
FAQ
Is x402 only for AI agents?
No. The protocol is HTTP-native; scripts, backends, and agents all drive the same 402 → pay → retry loop. TRM's point is that on-chain records alone cannot tell those apart.
Does Kertivo implement the x402 facilitator?
No. Kertivo sells evidence on Base USDC (Check, Shield, Index, Claims, Logs); like any x402 seller, its own paid routes use a standard x402 facilitator to verify and settle payments. Call any paid Kertivo route unpaid to see a standard 402 (with a PAYMENT-REQUIRED header), then retry with payment via an x402 client SDK.
Are Index grades for sale?
No. Sellers cannot buy an A. Badges are free embeds of earned grades.
Do you cover Solana or other assets?
Kertivo's paid verify/grade rails documented in /llms.txt are Base mainnet native USDC today. The wider x402 ecosystem may use other networks; we do not invent coverage we do not ship.
Limits
- This guide summarizes public protocol docs and one TRM analysis — not investment advice or a market forecast.
- Kertivo reports evidence; it does not custody funds, sanction-screen counterparties, or guarantee future uptime.
- A settled payment never proves the seller's data is correct.