x402 Payment Protocol · Live on mainnet · Bazaar-listed
Agents don't open accounts. They pay per proof.
Any x402-capable agent can buy a post-quantum AI attestation for $0.005 USDC on Base — no API key, no signup, no invoice. One HTTP request pays for and returns an ML-DSA-65 signed record anchored to Hedera mainnet, verifiable by anyone, for free, forever. Machine-to-machine commerce producing machine-verifiable evidence.
Verify, mint, settle. A failed mint is never charged.
The endpoint speaks standard x402: an unpaid request returns a 402 with a machine-readable payment challenge — scheme, amount, asset, and pay-to address. The agent signs a USDC authorization, retries with the PAYMENT-SIGNATURE header, and the exchange is atomic in the direction that matters: payment is verified before the attestation is minted, and settled only after the mint succeeds.
Payment checked first
The signed USDC authorization is verified against the challenge — amount, asset, network, timeout — before any work is done.
Attestation created
ML-DSA-65 signature over the payload, Merkle-batched, anchored to Hedera Consensus Service. Payment metadata is ZK-sealed into the record.
Charged only on success
USDC settles on Base only after the mint completes. If the mint fails, the authorization is never executed — the agent keeps its money.
One request to see the challenge. Two to own a proof.
Discovery is machine-native too: the endpoint publishes a standard manifest at /.well-known/x402.json and is listed on the x402 Bazaar, where agent frameworks already index it.
The receipt is the product. And it outlives everyone.
Agent-to-agent commerce has a bootstrap problem: autonomous buyers can't fill out signup forms, and autonomous sellers can't invoice them. x402 solves the payment half. Rubric solves the other half — proof that the transaction and the work behind it actually happened, in a record neither party can alter and neither party needs the other to verify.
Every paid attestation is a permanent public record: post-quantum signed, consensus-timestamped on Hedera, ZK-sealed payment metadata inside. An agent's operator, a counterparty, or an auditor in 2033 can check any record against the ledger — whether or not Rubric still exists.
Attestation as a primitive
Give your agent a receipts habit: every consequential decision it makes — or purchase it settles — gets a proof its operator can audit. x402-fetch, x402-axios, or raw HTTP.
Signed monthly statements
The /v1/x402/statement endpoint ($0.50) returns a signed monthly spend statement for one agent — totals, per-payment lines, Merkle root — itself an attestation anchored to HCS.
Don't trust this page
The settlement address is public. The anchor topic is public. The verifier is free. Check the live HCS stream ↗ yourself.
Outgrow the meter
Past ~200K attestations/month, the Enterprise tier is cheaper than paying per call — same records, same verification, plus dashboard, auditor portal, and SLA.