Attest

{
  "attestTx": "0x9c8b7a6f5e4d3c2b1a0f9e8d7c6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d9c8b",
  "attestationUrl": "https://base.easscan.org/attestation/view/0x5b4d0c1e8f7a4c2d9e0b6a3f1c8d7e6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d",
  "attester": "0xa11ce0000000000000000000000000000000a402",
  "block": "50829611",
  "chain": "eip155:8453",
  "data": {
    "payer": "0xb0b0000000000000000000000000000000000b0b",
    "priceUsd": 0.01,
    "responseSha256": "0x7d2a9b1c4e6f8a0b2c4d6e8f0a1b3c5d7e9f1a3b5c7d9e1f3a5b7c9d1e3f5a7b",
    "servedAt": "2026-09-03T15:16:06.000Z",
    "settlementNetwork": "eip155:8453",
    "settlementTx": "0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb",
    "slug": "crypto-price"
  },
  "eas": "0x4200000000000000000000000000000000000021",
  "existing": false,
  "schema": "string slug,bytes32 responseSha256,string settlementNetwork,string settlementTx,string payer,uint64 servedAt,uint64 priceMicroUsd",
  "schemaUid": "0x2a4e6c8d0f1b3a5c7e9d1f3b5a7c9e1d3f5b7a9c1e3d5f7b9a1c3e5d7f9b1a3c",
  "uid": "0x5b4d0c1e8f7a4c2d9e0b6a3f1c8d7e6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d",
  "verify": {
    "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",
    "payment": "follow settlementTx on eip155:8453: the payer paid this server's payTo",
    "responseDigest": "sha256 over the exact JSON bytes you received for that call; compare with responseSha256"
  }
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://agent402.tools/api/attest' \
  -H 'content-type: application/json' \
  --data-raw '{"tx":"0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb"}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://agent402.tools/api/attest' \
  -H 'content-type: application/json' \
  --data-raw '{"tx":"0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb"}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.05 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.05" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.05 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fagent402.tools%2Fapi%2Fattest&method=POST
const res = await pay("https://agent402.tools/api/attest", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "tx": "0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb"
  }),
});
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.05 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.05"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://agent402.tools/api/attest",
        json={
            "tx": "0x2f1fecade9bd945e7817c11e5a34cafe6b349dd8c92a7587efed1de476bddfeb",
        },
    )
    print(res.status_code, res.text)