Policy Check checkId Lookup via x402 Wire v2: A Technical Tutorial

Every Policy Check decision returns a checkId — a UUID identifying that exact decision, at that exact moment. This endpoint re-fetches a prior decision by that ID, without re-running the identity lookup, reputation scan, or payment-challenge scan a second time. This is a tutorial for its x402 wire v2 endpoint.

Why a Separate Endpoint

A Policy Check decision is a snapshot: the counterparty's identity, reputation, and payment challenge as they existed at scannedAt. If you need to hand that decision to another part of your system — an audit log, a second service in your pipeline, a human reviewer — re-running the full check would both cost another $0.02 and potentially return a different result if anything about the counterparty changed in between. The checkId lookup returns the exact original decision, unchanged, for free re-reads by anyone who has the ID.

The Endpoint

GET /api/v1/policy-check/x402-v2/{checkId}
Price: $0.02 per call

Note the path shape: x402-v2 comes before the checkId segment, not after — /api/v1/policy-check/x402-v2/{checkId}, not /api/v1/policy-check/{checkId}/x402-v2. Putting it after would read as "the v2 version of this specific check," which isn't what changes here; only the payment challenge for this lookup call does.

The 402 Challenge

curl -i https://contextiq.trango-compute.com/api/v1/policy-check/x402-v2/8875a324-9577-48f8-b506-877c26500a7e

{
  "x402Version": 2,
  "resource": { "url": "https://contextiq.trango-compute.com/api/v1/policy-check/x402-v2/8875a324-9577-48f8-b506-877c26500a7e" },
  "accepts": [{ "scheme": "exact", "network": "eip155:8453", "amount": "20000", "payTo": "0x4eba5ea3cf0f3fc307099317e17e54390f7a4c58", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" }],
  "extensions": { "bazaar": { "info": { "input": { "type": "http", "method": "GET" } } } }
}

This is a GET, unlike most of ContextIQ's other v2 routes — there's no request body, the checkId is entirely carried in the URL path.

Option A: API Key

curl https://contextiq.trango-compute.com/api/v1/policy-check/x402-v2/8875a324-9577-48f8-b506-877c26500a7e \
  -H "Authorization: Bearer sk_live_..."

Option B: Pay With x402, No API Key

import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";
import { wrapFetchWithPayment } from "@x402/fetch";

const account = privateKeyToAccount(process.env.WALLET_PRIVATE_KEY as `0x${string}`);
const client = createWalletClient({ account, transport: http(), chain: base });
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

const res = await fetchWithPayment(
  "https://contextiq.trango-compute.com/api/v1/policy-check/x402-v2/8875a324-9577-48f8-b506-877c26500a7e"
);

console.log(await res.json());

The Response

{
  "checkId": "8875a324-9577-48f8-b506-877c26500a7e",
  "endpoint": "https://contextiq.trango-compute.com/api/v1/token-inspector/pricing/x402-v2",
  "agentId": null,
  "network": "base",
  "createdAt": "2026-09-11T00:00:00.000Z",
  "decision": "allow",
  "score": 45,
  "maxScore": 50
}

This returns the summary fields from the original decision, not the full reasons[]/payment/identity breakdown — if you need the complete original response, keep it when you first receive it; the checkId lookup is for confirming the decision's headline outcome later, not for retrieving the full audit trail. If the checkId doesn't exist (wrong ID, or it's from a different account), you get a 404.

Try It

Combine this with the decision endpoint and receipt verification for the full pre-payment → pay → verify cycle, or open Policy Check directly.