ToolVet
80trust / 100

X402 Service Change Snapshot

by Agent Mercantile in Onchain & crypto

x402 APIPassing, checked 3 h ago

Determine whether a previously accepted x402 service payment contract is still equivalent enough to proceed. Compares one live unpaid 402 challenge, using a caller-supplied GET or POST request shape, against a caller-held baseline bound to that request identity. Not uptime monitoring, a trust score, a webhook, a marketplace crawl, or a generic POST {} probe of every x402 resource.

POST
https://api.agentmercantile.com/v1/x402-service-change-snapshot
Price
$0.01
per call in USDC
Uptime
100%
last 30 days
Response time
288 ms
712 ms slowest 5%
Last check
Passed
3 h ago, next any minute now

Run a free test callHow to call it

Reliability

All checks passedSome failedAll failedNot checked

Status and outage history · Atom feed · Watch with other listings

How to call it

POST https://api.agentmercantile.com/v1/x402-service-change-snapshot

Each call costs $0.01 in USDC on Base, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

POST https://api.agentmercantile.com/v1/x402-service-change-snapshot
content-type: application/json

{
  "method": "POST",
  "resource_url": "https://api.agentmercantile.com/v1/url-context"
}

Parameters

ParameterTypeRequiredDescription
baselineobjectNoOptional caller-held reusable payment-contract baseline bound to this request identity.
bodyobjectNoOptional JSON object for POST probes only.
methodstringYesRequired unpaid 402 probe method. Not inferred from discovery. One of: GET, POST.
resource_urlstring (uri)YesOne public HTTPS x402 resource URL on port 443.

Example response

The provider's example. We can't check it without paying.

{
  "decision": "BASELINE_CREATED",
  "limitations": [
    "Caller holds the baseline. Direct-service 402 is payment authority."
  ],
  "machine": "VM08",
  "methodology_version": "x402-service-change-snapshot-0.1.0",
  "status": "OK"
}

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.01.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://api.agentmercantile.com/v1/x402-service-change-snapshot' \
  -H 'content-type: application/json' \
  --data-raw '{"method":"POST","resource_url":"https://api.agentmercantile.com/v1/url-context"}'

# 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://api.agentmercantile.com/v1/x402-service-change-snapshot' \
  -H 'content-type: application/json' \
  --data-raw '{"method":"POST","resource_url":"https://api.agentmercantile.com/v1/url-context"}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// 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%2Fapi.agentmercantile.com%2Fv1%2Fx402-service-change-snapshot&method=POST
const res = await pay("https://api.agentmercantile.com/v1/x402-service-change-snapshot", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "method": "POST",
    "resource_url": "https://api.agentmercantile.com/v1/url-context"
  }),
});
console.log(res.status, await res.text());
Python: pay and call
# 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://api.agentmercantile.com/v1/x402-service-change-snapshot",
        json={
            "method": "POST",
            "resource_url": "https://api.agentmercantile.com/v1/url-context",
        },
    )
    print(res.status_code, res.text)

Security scan

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