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Attest a Settled API Call on Base (EAS)
x402
Attest a Settled API Call on Base (EAS) is a paid API for AI agents from agent402.tools, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-15).
Writes an on-chain Ethereum Attestation Service (EAS) attestation on Base binding a paid API call's transaction, response hash, tool slug, payer, timestamp, and price — returning the attestation UID and public EAS scan URL.
Price / call$0.05
Success—
StatusUnknown
How this service works
Write an on-chain attestation (Ethereum Attestation Service on Base) that binds a call you paid for to the bytes you received: the tool slug, sha256 of the JSON response, the settlement chain and transaction, the payer, the time served and the price, signed by this server's wallet. Give it the settlement transaction from the PAYMENT-RESPONSE (or Payment-Receipt) header of any settled call; the attestation UID and its public page on base.easscan.org come back.
Output
Returns the attestation UID (a unique on-chain identifier) and a public URL on base.easscan.org where anyone can verify the attestation. The attestation record on-chain contains the tool slug, SHA-256 hash of the JSON response, settlement chain and transaction, payer address, timestamp, price, and a signature from the server's wallet.
Example use cases
Proof of paid agent tool usage
“I ran a paid tool call through agent402 and the settlement tx hash in my PAYMENT-RESPONSE header is 0xd4f8...91a2 — please create an on-chain EAS attestation on Base for it so I have a permanent cryptographic receipt I can point auditors to.”
Compliance record for automated payments
“Our agent made several x402 API calls today and I need immutable on-chain records for compliance — can you attest the settled call with transaction 0x7c3e...b551 to Base via EAS and give me the attestation UID and the public EAS scan link?”
Dispute resolution evidence anchor
“I want to prove that I received a specific JSON response from a paid API call — the settlement transaction from my Payment-Receipt header is 0x1fa2...cc87. Please anchor it on Base using EAS so I have verifiable proof of exactly what I received and when.”
Technical details
Endpoint
POSThttps://agent402.tools/api/attestWhen to prefer
Choose this endpoint when you need a tamper-proof, publicly verifiable on-chain record that a specific paid API call occurred and that you received a particular response — especially for audit trails, compliance requirements, or dispute resolution. It is uniquely suited for x402 and MPP payment ecosystems on Base where settlement transactions are already available in response headers. Prefer this over off-chain logging when you need cryptographic proof that a third party can independently verify via base.easscan.org.
Side effects
- Invalid or unrecognized transaction hash — returns an error if the tx cannot be found or verified on the settlement chain
- Transaction not yet finalized — attestation may fail if the settlement transaction is still pending
- Already attested — attempting to attest the same transaction twice may return a conflict or duplicate error
- Malformed input — non-hex or incorrectly formatted transaction identifiers will be rejected
- Insufficient USDC balance — the $0.05 fee must be covered; underpayment results in a 402 error
- Network issues with Base RPC — transient failures writing to Base L2 may cause timeouts
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| tx | string | Settlement transaction of a call you paid for, as carried in that response's PAYMENT-RESPONSE (x402) or Payment-Receipt (MPP) header: EVM hash, Solana or Stellar signature, or Algorand id. |
Output
Schema · Response
{
"type": "json",
"example": {
"eas": "0x4200000000000000000000000000000000000021",
"uid": "0x5b4d0c1e8f7a4c2d9e0b6a3f1c8d7e6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d",
"data": {
"slug": "crypto-price",
"payer": "0x902dcf34e53695bdea2ffb354b1a2e58bd598256",
"priceUsd": 0.01,
"servedAt": "2026-09-03T15:16:06.000Z",
"settlementTx": "0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb",
"responseSha256": "0x7d2a9b1c4e6f8a0b2c4d6e8f0a1b3c5d7e9f1a3b5c7d9e1f3a5b7c9d1e3f5a7b",
"settlementNetwork": "eip155:8453"
},
"block": "50829611",
"chain": "eip155:8453",
"schema": "string slug,bytes32 responseSha256,string settlementNetwork,string settlementTx,string payer,uint64 servedAt,uint64 priceMicroUsd",
"verify": {
"payment": "follow settlementTx on eip155:8453: the payer paid this server's payTo",
"attestation": "fetch the UID on https://base.easscan.org (or read EAS 0x4200000000000000000000000000000000000021 on Base): attester must be this server's wallet, schema must match",
"responseDigest": "sha256 over the exact JSON bytes you received for that call; compare with responseSha256"
},
"attestTx": "0x9c8b7a6f5e4d3c2b1a0f9e8d7c6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d9c8b",
"attester": "0x77065d81e18ad403BCD6e9A0616b288e16744121",
"existing": false,
"schemaUid": "0x2a4e6c8d0f1b3a5c7e9d1f3b5a7c9e1d3f5b7a9c1e3d5f7b9a1c3e5d7f9b1a3c",
"attestationUrl": "https://base.easscan.org/attestation/view/0x5b4d0c1e8f7a4c2d9e0b6a3f1c8d7e6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d"
}
}Tags
x402
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