x402 GPT API | GPT-5.6 Luna Base USDC Gateway

GPT55 is an x402 GPT API gateway: it provides an OpenAI-compatible GPT-5.6 Luna Standard result for $0.00293 USDC on Base. This is a compatible gateway, not an OpenAI-operated product. Buyers can pay one request from a browser wallet without handing over a private key, or use the quote-first agent fallback client when a wallet UI is unavailable.

The focused search topic is x402 GPT API / GPT API with USDC on Base: one POST request, one live quote, and one response. The canonical buyer path and complete integration guide are below.

The EVM Wallet Balance Snapshot remains available as a separate utility alternative; it is not the model product.

Canonical service entry:

• Service hub: https://gpt55.558686.xyz/x402/service

• Machine-readable catalog: https://gpt55.558686.xyz/x402/service.json

• x402 GPT API guide: https://gpt55.558686.xyz/x402/guides/ai-agent-x402-api

• Main model route: POST https://gpt55.558686.xyz/v1/chat/completions/standard

• Browser checkout: https://gpt55.558686.xyz/x402/service?checkout=standard-chat

• Wallet alternative: https://gpt55.558686.xyz/x402/service?checkout=evm-wallet-balance

• Key Pack upgrade: https://x402-key.558686.xyz/x402/checkout

• MCP endpoint: https://gpt55.558686.xyz/mcp

For the exact browser-wallet, Base MCP, agent fallback, receipt, and directory verification sequence, see docs/demand-first-checkout.md.

Agent Fallback

The buyer client is quote-only by default. Its local policies pin the exact URL, HTTP method, amount, Base network, canonical Base USDC contract, and merchant address for both Wallet and Standard. Remote catalogs are discovery metadata only. The client does not sign or pay unless the operator explicitly sets PAY_REAL_X402=1 and provides a wallet key in the operator-controlled process.

Never paste a private key, seed phrase, payment header, API key, or exchange credential into a website, chat, issue, log, or remote service.

Related MCP server: Blocksize Market Data

Quote-Only Check

git clone https://github.com/wangletiand/gpt55-x402-gateway.git
cd gpt55-x402-gateway
npm install
ROUTE_ID=standard MAX_USDC=0.00293 npm run first-payment:quote

The command remains quote-only unless real payment is explicitly enabled. Generated evidence files and .env files are ignored by Git.

The live quote is authoritative immediately before any payment. For an OpenAI-compatible request, send the same JSON body to /v1/chat/completions/standard after the x402 client returns a valid paid retry. The public service hub includes the browser-wallet flow and a link to the agent fallback client.

Local MCP Wrapper

npm install
npm test
npm start

The wrapper exposes one local read-only directory tool. It does not proxy MCP tool calls, custody funds, store wallet keys, or execute payments.

Repository Scope

This public repository intentionally contains only the maintained runtime wrapper, buyer safety client, tests, and concise documentation. Operational logs, payment evidence, wallet files, credentials, internal channel ledgers, and bulk submission automation are excluded.

Support and Security

For security reports, follow SECURITY.md. Do not include secrets or wallet material in a report.

Licensed under the MIT License.