Preflight

{
  "agentVerdict": {
    "browserLikelyRequired": false,
    "confidence": "high",
    "reasons": [
      "At least one static GET/POST form can be described from the initial HTML without executing page JavaScript."
    ],
    "verdict": "http_candidate"
  },
  "fetchedAt": "2026-09-23T10:00:00.000Z",
  "finalUrl": "https://example.com/contact",
  "forms": [
    {
      "action": "https://example.com/contact/submit",
      "enctype": "application/x-www-form-urlencoded",
      "fieldCount": 4,
      "fields": [
        {
          "autocomplete": "email",
          "checked": false,
          "disabled": false,
          "id": "contact-email",
          "label": "Email address",
          "max": null,
          "maxLength": 254,
          "min": null,
          "minLength": null,
          "multiple": false,
          "name": "email",
          "options": null,
          "pattern": null,
          "placeholder": "[email protected]",
          "required": true,
          "selectedValues": null,
          "step": null,
          "type": "email",
          "value": ""
        },
        {
          "autocomplete": null,
          "checked": false,
          "disabled": false,
          "id": "plan",
          "label": "Plan",
          "max": null,
          "maxLength": null,
          "min": null,
          "minLength": null,
          "multiple": false,
          "name": "plan",
          "options": [
            {
              "disabled": false,
              "label": null,
              "selected": false,
              "text": "Basic",
              "value": "basic"
            },
            {
              "disabled": false,
              "label": null,
              "selected": true,
              "text": "Pro",
              "value": "pro"
            }
          ],
          "pattern": null,
          "placeholder": null,
          "required": true,
          "selectedValues": [
            "pro"
          ],
          "step": null,
          "type": "select",
          "value": "pro"
        }
      ],
      "hasFileUpload": false,
      "hasPasswordField": false,
      "index": 0,
      "method": "POST",
      "standardHttpSubmission": true,
      "submitControls": 1
    }
  ],
  "http": {
    "contentType": "text/html; charset=utf-8",
    "redirectCount": 0,
    "status": 200
  },
  "limitations": [
    "Static initial HTML only; page JavaScript is not executed.",
    "Use agentVerdict.verdict for the preferred three-state routing result; browserLikelyRequired remains for backward compatibility and false can also mean undetermined.",
    "This service inspects structure only and does not submit forms or perform actions."
  ],
  "networkSafety": {
    "fetchDnsChecks": 2,
    "initialDnsCheck": {
      "addressCount": 2,
      "allPublic": true,
      "families": [
        4,
        6
      ]
    },
    "postFetchDnsPublicRecheck": true,
    "redirectTargetsRechecked": true
  },
  "page": {
    "captchaMarkers": [],
    "formsFound": 1,
    "iframeCount": 0,
    "scriptCount": 2,
    "spaMarkers": []
  },
  "requestedUrl": "https://example.com/contact"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://zeroworker-web-action-api.zeroworker-lab.workers.dev/v1/preflight' \
  -H 'content-type: application/json' \
  --data-raw '{"url":"https://example.com/contact"}'

# 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://zeroworker-web-action-api.zeroworker-lab.workers.dev/v1/preflight' \
  -H 'content-type: application/json' \
  --data-raw '{"url":"https://example.com/contact"}' \
  | 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 $0.002 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.002" });
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 $0.002 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fzeroworker-web-action-api.zeroworker-lab.workers.dev%2Fv1%2Fpreflight&method=POST
const res = await pay("https://zeroworker-web-action-api.zeroworker-lab.workers.dev/v1/preflight", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "url": "https://example.com/contact"
  }),
});
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 $0.002 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.002"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://zeroworker-web-action-api.zeroworker-lab.workers.dev/v1/preflight",
        json={
            "url": "https://example.com/contact",
        },
    )
    print(res.status_code, res.text)