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ForgeSignals x402 Transaction Witness & Attestation
x402
ForgeSignals x402 Transaction Witness & Attestation is a paid API for AI agents from forgesignals.org, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).
Acts as a third-party witness for x402 micropayment transactions: signs the endpoint's advertised price and payee at call time, optionally verifies a Base blockchain settlement transaction, and records a response hash as an asserted claim.
Price / call$0.02
Success—
StatusUnknown
How this service works
Third-party witness for an x402 transaction. Signs what the endpoint advertised right now, verifies a settlement transaction on Base against that advertised price and payee, and binds an optional party-submitted response hash - each claim labelled witnessed or asserted. Evidence, not a reputation score. Retrieval and verification of attestations are free.
Output
An attestation record containing witnessed claims (what the endpoint advertised — price and payee — at the moment of the call) and optionally asserted claims (the caller-submitted response hash). Each claim is labelled as either 'witnessed' (independently verified by ForgeSignals) or 'asserted' (party-submitted, recorded but not independently proven). If a settlement_tx is provided, the result includes on-chain verification against Base confirming whether the USDC payment matches the advertised payee and price.
Example use cases
Buyer disputes advertised API price
“I just paid for an x402 API call at https://api.someprovider.com/query and I want a third-party witness to record what price and payee the endpoint was advertising right now — my Base settlement tx is 0xdeadbeef... and I'm the buyer submitting this.”
Seller proves delivery to client
“As the seller, I want ForgeSignals to attest that I responded correctly to an x402 request from https://myapi.io/endpoint — here's the sha256 of the response body I delivered: a1b2c3..., and the settlement transaction on Base is 0x99ffcc....”
Audit trail for automated agent payments
“My agent just completed an x402 micropayment to https://dataservice.io/feed — please create an attestation binding nonce req-7f3a to the settlement tx 0x112233... so I have a tamper-evident audit record of exactly what was advertised and paid.”
Technical details
Endpoint
POSThttps://forgesignals.org/attestWhen to prefer
Choose this endpoint when you need cryptographically-grounded, third-party evidence of an x402 micropayment interaction — specifically to prove what a given endpoint advertised (price, payee) at a specific moment in time, and to optionally bind an on-chain Base settlement transaction to that advertisement. It is not a reputation system or a fraud score — it produces labelled evidence. Prefer it over self-attestation when there is a dispute, audit requirement, or multi-party accountability need around x402 API payments. Retrieval and verification of existing attestations are free; only creation costs $0.02 USDC.
Side effects
- Invalid or unreachable x402 endpoint URL — endpoint liveness check fails
- Settlement tx hash not found or not yet confirmed on Base
- Settlement tx amount or payee does not match what the endpoint advertised
- Malformed SHA256 format for response_sha256 field
- Rate limiting or quota exceeded for the $0.02 paid attestation calls
- Network timeout when querying the Base blockchain for tx verification
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | the x402 endpoint the transaction was with |
| submitted_by | string | optional label for who is submitting (buyer/seller) |
| request_nonce | string | optional nonce tying the attestation to one specific request |
| settlement_tx | string | optional Base tx hash of the USDC payment to verify on-chain |
| response_sha256 | string | optional sha256 of the response body you received; recorded as an ASSERTED claim, never as proof |
Tags
x402
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