Preflight

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://verifier.quantumshieldlabs.dev/x402/preflight' \
  -H 'content-type: application/json' \
  --data-raw '{"action_type":"purchase","authority_scope":{"allowed_action_types":["purchase"],"denied_action_types":["withdraw"],"human_approval_action_types":["transfer"]},"constraints":{"max_spend_usd":"5.00","prohibited_destinations":["blocked-market.example"],"required_evidence":["inventory_check"]},"evidence_items":[{"name":"inventory_check","result":true}],"operation_id":"purchase-42","requested_action":{"description":"Buy an approved test asset","destination":"approved-market.example","spend_usd":"4.50"}}'

# 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://verifier.quantumshieldlabs.dev/x402/preflight' \
  -H 'content-type: application/json' \
  --data-raw '{"action_type":"purchase","authority_scope":{"allowed_action_types":["purchase"],"denied_action_types":["withdraw"],"human_approval_action_types":["transfer"]},"constraints":{"max_spend_usd":"5.00","prohibited_destinations":["blocked-market.example"],"required_evidence":["inventory_check"]},"evidence_items":[{"name":"inventory_check","result":true}],"operation_id":"purchase-42","requested_action":{"description":"Buy an approved test asset","destination":"approved-market.example","spend_usd":"4.50"}}' \
  | 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 $0.005 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.005" });
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 $0.005 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fverifier.quantumshieldlabs.dev%2Fx402%2Fpreflight&method=POST
const res = await pay("https://verifier.quantumshieldlabs.dev/x402/preflight", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "action_type": "purchase",
    "authority_scope": {
      "allowed_action_types": [
        "purchase"
      ],
      "denied_action_types": [
        "withdraw"
      ],
      "human_approval_action_types": [
        "transfer"
      ]
    },
    "constraints": {
      "max_spend_usd": "5.00",
      "prohibited_destinations": [
        "blocked-market.example"
      ],
      "required_evidence": [
        "inventory_check"
      ]
    },
    "evidence_items": [
      {
        "name": "inventory_check",
        "result": true
      }
    ],
    "operation_id": "purchase-42",
    "requested_action": {
      "description": "Buy an approved test asset",
      "destination": "approved-market.example",
      "spend_usd": "4.50"
    }
  }),
});
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 $0.005 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.005"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://verifier.quantumshieldlabs.dev/x402/preflight",
        json={
            "action_type": "purchase",
            "authority_scope": {
                "allowed_action_types": [
                    "purchase",
                ],
                "denied_action_types": [
                    "withdraw",
                ],
                "human_approval_action_types": [
                    "transfer",
                ],
            },
            "constraints": {
                "max_spend_usd": "5.00",
                "prohibited_destinations": [
                    "blocked-market.example",
                ],
                "required_evidence": [
                    "inventory_check",
                ],
            },
            "evidence_items": [
                {
                    "name": "inventory_check",
                    "result": True,
                },
            ],
            "operation_id": "purchase-42",
            "requested_action": {
                "description": "Buy an approved test asset",
                "destination": "approved-market.example",
                "spend_usd": "4.50",
            },
        },
    )
    print(res.status_code, res.text)