Plumb Data Exchange

Free. Cross-check a seller's signed x402 offer + receipt (offer-and-receipt extension): verifies the signatures (official x402 functions; pin the seller with sellerAddress for EIP-712 or sellerJwk for JWS), checks offer and receipt agree, and returns the exact `claim` to prove with verify_payment. Pass that verification's checkId to learn which side failed.

Convert a table to CSV without changing any value; verified by round-trip. Costs $0.05 USDC (x402).

Free. The exchange's on-ledger ProvenPayer credential (XLS-70): issued to an XRPL account after 2 settled, Plumb-proven payments to the house; readable by any seller with ledger_entry. Returns the account's standing, the issued credential (with the CredentialCreate hash, provable with plumb-xrpl), how to accept it, and the challenge format for the holder unlock.

Remove duplicate rows by exact key, keeping the first or last, and report conflicting columns per group. Costs $0.05 USDC (x402).

Free. Status and (once verified) the result of a paid job, using the accessToken its paid call returned.

Free. Current state of a verification by checkId; re-checks it once its retry or challenge time has passed.

Free. Up to 50 checks at once (re-checked when due), as rows; format "csv" adds a reconciliation CSV.

Prove any XRP Ledger transaction without trusting a server: validator-list quorum, hash links, rebuilt tx tree. Returns full fields, metadata (balances, escrows, channels, credentials as of the tx), quorum evidence and a signed receipt. Unvalidated tx keeps your payment.

Compare two versions of a table by key: rows added, removed and changed (with the changed columns). Costs $0.05 USDC (x402).

Free: the same verification as verify_payment, limited to 3 NEW claims per client per day (asking again about a claim already checked is always free). Holders of the exchange's on-ledger ProvenPayer credential get more: pass xrplProof (see credential_status).

Verify an on-chain payment without trusting any RPC: did this tx transfer at least this amount of a token (default USDC) to this payee, optionally from this payer? Proven by Plumb (Base via proof-backed L1 checkpoints, Ethereum via a light client, XRP Ledger via a quorum of Ripple's validator list: RLUSD, XRP or any issued currency). Bound to the exact transfer (log index); returns the proof level, how long a Base checkpoint can still be challenged, the evidence to re-check, and an Ed25519-signed receipt. Never answers not_paid while a payment is still pending; abstains (unverifiable) whenever the proof is incomplete. Costs $0.02 USDC (x402) ($0.002 for an XRP Ledger payment); asking again about the same claim costs nothing. Optional requiredLevel (releasable or not) and callbackUrl (signed events when the level is reached, the answer changes, or checking gives up).

Verify up to 25 payments in one call for $0.25 ($0.05 when every claim is on the XRP Ledger) USDC (x402): give `claims` (same fields as verify_payment) or `csv` (header: chain,txHash,payee,token,minAmountRaw,payer,logIndex,invoiceId). Claims already checked cost nothing; if all of them were, nothing is charged. Returns one row per claim (format "csv" adds a reconciliation CSV).

Free for a PAID check: add a callback (https) that receives signed events when requiredLevel is reached, when the answer changes, when it becomes final, or when checking gives up. The service re-checks on its own.

What should I build? x402 agent demand by category from public chain data (Base USDC + XRPL), with fake demand removed (testers, sellers paying themselves, loops; wallet fleets counted as one buyer) and gaps ranked (repeat buyers per seller). Rolling 7 days, refreshed every 2 h. Signed answer with sample transactions you can check, plus a dashboard link.