Blockchain Data · x402

Buyer-side payment firewall: should THIS agent make THIS payment now

by 402sentinel.com · discovered, not yet claimed by its owner · updated 2026-09-30

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Buyer-side payment firewall: should THIS agent make THIS payment now? Where /api/assess vets the seller, this vets the payment against your own agent's behaviour. POST {agent_id, payment:{payto_address,amount,resource_url}, context?:{untrusted_text,intended}, policy?} returns allow/hold/block plus 9 signals incl. routing_anomaly, velocity, amount_anomaly, injection_destination, intent_mismatch. Stateful per agent_id.

Tags: bazaar

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/57271.json for the price and payment options.
Pay. Call GET https://402sentinel.com/api/firewall. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, Solana, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.002 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base, Solana
Calls (30d): 2 · 1 unique payers (third-party data from the public x402 Bazaar)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.002	0x1A9Fa76f5b420e85DE147C4419638BEbE64D6dE5	300s
exact	Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp	USDC	$0.002	4uLqY8BnJuA7CFxRork2FnNMu2u9NsJquF8Cc6V5B5jB	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x1A9Fa76f5b420e85DE147C4419638BEbE64D6dE5",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "4uLqY8BnJuA7CFxRork2FnNMu2u9NsJquF8Cc6V5B5jB",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  }
]

Examples

curl

curl "https://402sentinel.com/api/firewall"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://402sentinel.com/api/firewall");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://402sentinel.com/api/firewall")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: 402sentinel.com
Endpoint: https://402sentinel.com/api/firewall
Machine-readable: /resources/57271.json