The low-friction first purchase is one EVM Wallet Balance Snapshot for a public Base or Ethereum address. It reads public chain state and never needs a buyer private key:
| Field | Live contract |
|---|---|
| Checkout | https://gpt55.558686.xyz/x402/service?checkout=evm-wallet-balance |
| Paid request | GET https://gpt55.558686.xyz/v1/tools/evm-wallet-balance |
| Public inputs | EVM_ADDRESS and EVM_NETWORK=base or ethereum |
| Price | $0.001 (1000 atomic USDC) |
| Network and asset | Base eip155:8453, canonical USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 |
| Recipient | 0x1f0130669ca6fd02e025a984cc038f139df19a2f |
| Delivery | Address, network, native balance, USDC balance, readiness fields, and receipt headers |
The live HTTP 402 Payment Required response is authoritative immediately
before payment. Directory metadata is discovery only; a buyer must verify the
amount, network, asset, recipient, method, and complete resource URL in that
response.
Open the Wallet checkout in a browser with an injected Base wallet and choose Pay with browser wallet. The wallet signs the exact USDC authorization in the browser. A private key never leaves the buyer’s wallet or runtime. The checkout retries the same request, returns HTTP 200, and exposes the receipt only after a successful settlement.
Base MCP buyers can use its x402 flow with a tight cap. The first call reads the live quote; the second completes the approved request:
initiate_x402_request(
url="https://gpt55.558686.xyz/v1/tools/evm-wallet-balance?address=0x1111111111111111111111111111111111111111&network=base",
method="GET",
maxPayment="0.001"
)
complete_x402_request(requestId="<requestId from the first call>")
The buyer should approve only a quote at or below the cap and should require a
successful PAYMENT-RESPONSE (or X-PAYMENT-RESPONSE) plus the service
receipt before treating the result as delivered.
The repository client is quote-only until the buyer explicitly opts into a buyer-owned payment runtime:
npm install @x402/fetch @x402/core @x402/evm viem
EVM_ADDRESS=0x1111111111111111111111111111111111111111 EVM_NETWORK=base MAX_USDC=0.001 npm run first-payment:quote
The quote response uses PAYMENT-REQUIRED. A payment-capable client signs
locally, retries the same request with PAYMENT-SIGNATURE (or
X-PAYMENT), and accepts delivery only after HTTP 200, a successful settlement
response, and x-x402-receipt-id plus x-x402-receipt-url.
GPT-5.6 Luna Standard remains available for buyers who need a model result:
| Field | Live contract |
|---|---|
| Checkout | https://gpt55.558686.xyz/x402/service?checkout=standard-chat |
| Paid request | POST https://gpt55.558686.xyz/v1/chat/completions/standard |
| Price | $0.00293 (2930 atomic USDC) |
Quote it without payment using:
ROUTE_ID=main-model-standard MAX_USDC=0.003 npm run first-payment:quote
The Standard endpoint retains its existing 402 Index registration for URL and directory continuity:
402 Index’s Bazaar v2 record uses live x402 v2 fields (accepts[].amount and
the top-level/resource description). Wallet discovery is also published by the
live service and current CDP/Agentic.Market metadata. Older directory cards may
still show stale copy, so buyers must re-fetch the selected endpoint before
paying.
This document describes the public buyer contract only. It contains no wallet seed, private key, payment header, or credential.