Preflight Payment

{
  "checks": [
    {
      "evidence_digest": null,
      "id": "amount-within-max",
      "result": "PASS",
      "summary": "The proposed amount is within the caller-configured maximum."
    }
  ],
  "decision": {
    "authorized": true,
    "reasons": [
      "All configured policy checks passed."
    ],
    "status": "ALLOW"
  },
  "receipt": {
    "proof": {
      "algorithm": "ed25519",
      "key_id": "ed25519-EXAMPLEKEY000000",
      "signature": "UN4TzBvkRsf0eGm4…ZFyElhq1Cg",
      "signed": true
    },
    "receipt": {
      "receipt_id": "OCD-RCP-EXAMPLE-0000-0000-0000",
      "receipt_type": "PREFLIGHT"
    },
    "schema": "onchaindiligence.public-action-receipt.v1"
  }
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://mcp.onchaindiligence.com/x402/preflight-payment' \
  -H 'content-type: application/json' \
  --data-raw '{"action":{"amount":"1.00","asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","kind":"PAYMENT","network":"eip155:8453","recipient":"0x000000000000000000000000000000000000dEaD","resource":"https://service.example/api","sender":null},"options":{"screen_recipient_sanctions":true},"policy":{"allowed_assets":["0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"],"allowed_networks":["eip155:8453"],"allowed_resource_origins":["https://service.example"],"expected_recipient":null,"max_amount":"5.00"},"references":{"mandate_digest":null}}'

# 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://mcp.onchaindiligence.com/x402/preflight-payment' \
  -H 'content-type: application/json' \
  --data-raw '{"action":{"amount":"1.00","asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","kind":"PAYMENT","network":"eip155:8453","recipient":"0x000000000000000000000000000000000000dEaD","resource":"https://service.example/api","sender":null},"options":{"screen_recipient_sanctions":true},"policy":{"allowed_assets":["0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"],"allowed_networks":["eip155:8453"],"allowed_resource_origins":["https://service.example"],"expected_recipient":null,"max_amount":"5.00"},"references":{"mandate_digest":null}}' \
  | 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 $0.01 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.01" });
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 $0.01 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fmcp.onchaindiligence.com%2Fx402%2Fpreflight-payment&method=POST
const res = await pay("https://mcp.onchaindiligence.com/x402/preflight-payment", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "action": {
      "amount": "1.00",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "kind": "PAYMENT",
      "network": "eip155:8453",
      "recipient": "0x000000000000000000000000000000000000dEaD",
      "resource": "https://service.example/api",
      "sender": null
    },
    "options": {
      "screen_recipient_sanctions": true
    },
    "policy": {
      "allowed_assets": [
        "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"
      ],
      "allowed_networks": [
        "eip155:8453"
      ],
      "allowed_resource_origins": [
        "https://service.example"
      ],
      "expected_recipient": null,
      "max_amount": "5.00"
    },
    "references": {
      "mandate_digest": null
    }
  }),
});
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 $0.01 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.01"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://mcp.onchaindiligence.com/x402/preflight-payment",
        json={
            "action": {
                "amount": "1.00",
                "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
                "kind": "PAYMENT",
                "network": "eip155:8453",
                "recipient": "0x000000000000000000000000000000000000dEaD",
                "resource": "https://service.example/api",
                "sender": None,
            },
            "options": {
                "screen_recipient_sanctions": True,
            },
            "policy": {
                "allowed_assets": [
                    "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
                ],
                "allowed_networks": [
                    "eip155:8453",
                ],
                "allowed_resource_origins": [
                    "https://service.example",
                ],
                "expected_recipient": None,
                "max_amount": "5.00",
            },
            "references": {
                "mandate_digest": None,
            },
        },
    )
    print(res.status_code, res.text)