Chain Address

{
  "data": {
    "ambiguous": false,
    "checksum": {
      "checksum_valid": true,
      "checksummed": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      "eip1191_applied": false,
      "input_form": "lowercase"
    },
    "matches": [
      {
        "chain": "evm",
        "detail": {},
        "format": "hex20",
        "reason": "no_checksum",
        "valid": true
      }
    ],
    "valid": true
  },
  "meta": {
    "computed_at": "2026-09-28T12:00:00.000Z",
    "deterministic": true,
    "disclaimer": "Factual output of a deterministic computation over public data. Provided as is, with no warranty of accuracy, completeness or availability. Not investment, financial, legal, tax, medical or any other professional advice, and not a recommendation. Verify before relying on it. Terms: https://api.duoleads.com/terms",
    "price_usd": "0.05",
    "request_id": "01K6B7Q4ZC8H3F2M9WXR5TYN0D"
  },
  "ok": true,
  "route": "/v1/chain/address",
  "version": "1.0.0"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://api.duoleads.com/v1/chain/address?address=0xd8da6bf26964af9d7eed9e03e53415d37aa96045'

# 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 - 'https://api.duoleads.com/v1/chain/address?address=0xd8da6bf26964af9d7eed9e03e53415d37aa96045' \
  | 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%2Fapi.duoleads.com%2Fv1%2Fchain%2Faddress
const res = await pay("https://api.duoleads.com/v1/chain/address?address=0xd8da6bf26964af9d7eed9e03e53415d37aa96045");
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.get("https://api.duoleads.com/v1/chain/address?address=0xd8da6bf26964af9d7eed9e03e53415d37aa96045")
    print(res.status_code, res.text)