Payee Check

{
  "mode": "payee-check",
  "paid_sats": 20,
  "payment_hash": "x402:<sha256 hex>",
  "receipt": {
    "payload": {
      "at": "<ISO 8601 time>",
      "kid": "<signing key id>",
      "mode": "payee-check",
      "payment_hash": "x402:<sha256 hex>",
      "v": 1,
      "verdict_sha256": "<sha256 hex of the verdict>"
    },
    "signature": "<base64url Ed25519 signature>"
  },
  "verdict": {
    "controls": {
      "domain_lookalike": false,
      "domain_unknown": false,
      "iban_differs": false,
      "iban_invalid": false,
      "ibans_found": 0,
      "referential_used": true
    },
    "decision": "ok",
    "instruction": "Pay according to the usual procedure.",
    "reasons": [],
    "rule": "freeze if the IBAN differs or the domain is a lookalike (safe checks, they override the engine) ; verify_callback if request for new bank >= 0.5, pressure >= 0.6, off-channel >= 0.5, or unknown sender ; otherwise ok",
    "scores": {
      "bank_change": 0.02,
      "nature": "normal_invoice",
      "off_channel": 0.02,
      "pressure": 0.02
    }
  }
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://verdict.kechlab.com/v1/payee-check' \
  -H 'content-type: application/json' \
  --data-raw '{"body":"Please find invoice 118 for 1250 EUR, due 30 November. Our payment details are unchanged.","known_supplier":{"domain":"fournisseur.fr","iban":"FR76 3000 6000 0112 3456 7890 189","name":"Fournisseur SA"},"sender":"[email protected]","subject":"Invoice 118"}'

# 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://verdict.kechlab.com/v1/payee-check' \
  -H 'content-type: application/json' \
  --data-raw '{"body":"Please find invoice 118 for 1250 EUR, due 30 November. Our payment details are unchanged.","known_supplier":{"domain":"fournisseur.fr","iban":"FR76 3000 6000 0112 3456 7890 189","name":"Fournisseur SA"},"sender":"[email protected]","subject":"Invoice 118"}' \
  | 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 $0.0494 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.0494" });
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 $0.0494 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fverdict.kechlab.com%2Fv1%2Fpayee-check&method=POST
const res = await pay("https://verdict.kechlab.com/v1/payee-check", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "body": "Please find invoice 118 for 1250 EUR, due 30 November. Our payment details are unchanged.",
    "known_supplier": {
      "domain": "fournisseur.fr",
      "iban": "FR76 3000 6000 0112 3456 7890 189",
      "name": "Fournisseur SA"
    },
    "sender": "[email protected]",
    "subject": "Invoice 118"
  }),
});
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 $0.0494 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.0494"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://verdict.kechlab.com/v1/payee-check",
        json={
            "body": "Please find invoice 118 for 1250 EUR, due 30 November. Our payment details are unchanged.",
            "known_supplier": {
                "domain": "fournisseur.fr",
                "iban": "FR76 3000 6000 0112 3456 7890 189",
                "name": "Fournisseur SA",
            },
            "sender": "[email protected]",
            "subject": "Invoice 118",
        },
    )
    print(res.status_code, res.text)