x402 GPT API: OpenAI-compatible GPT-5.6 Luna Standard on Base

Name: GPT55 x402 GPT API
Price: 0.00293 USD

GPT55 is an x402 GPT API for agents, scripts, and applications that need one OpenAI-compatible result without an API key, account, or subscription. The product is independent and is not operated by OpenAI.

Live contract: one POST /v1/chat/completions/standard request costs $0.00293 USDC (2930 atomic units) on Base eip155:8453. The live HTTP 402 response is authoritative immediately before payment.

Use case

Point an OpenAI-shaped client at a pay-per-call endpoint when a full API-key onboarding flow is unnecessary. The request body uses the familiar model and messages fields; successful delivery is an OpenAI-compatible JSON response with usage metadata and x402 receipt headers.

1. Inspect the quote

curl -i -X POST https://gpt55.558686.xyz/v1/chat/completions/standard \
  -H 'Content-Type: application/json' \
  -d '{"model":"gpt-5.6-luna","messages":[{"role":"user","content":"Reply with exactly: OK"}],"max_tokens":8}'

The response is 402 Payment Required. Confirm the amount is at most 0.00293 USDC, the network is Base, the asset is canonical Base USDC, and the recipient is the one shown in that live response.

2. Pay and retry from the buyer runtime

Use a buyer-owned browser wallet or a local x402 client. The private key stays in that wallet or local process. Retry the same URL, method, and body with the payment header returned by the client.

Open browser-wallet checkout
Quote-first client source
ROUTE_ID=standard MAX_USDC=0.00293 node first-payment-client.mjs runs the Standard route in quote-only mode; set PAY_REAL_X402=1 only in a buyer-owned wallet runtime after reviewing the live 402 quote.
See all current services and live prices

Accept the result only after HTTP 200 and a successful settlement response. Receipts are evidence of a delivered request; directory reads and quote probes are not purchases.

Lowest-friction canary

For a deterministic first payment, use the translate canary at POST https://gpt55.558686.xyz/v1/tools/translate with the same $0.00293 Base USDC cap. The quote-first command is:

ROUTE_ID=translate-canary MAX_USDC=0.00293 node first-payment-client.mjs

Read the translate canary buyer guide

FAQ

Is this an OpenAI API key replacement?: It is a separate OpenAI-compatible gateway. It does not issue OpenAI keys and is not an OpenAI-operated product.
What is the first-request price?: The current Standard route advertises $0.00293 USDC, or 2930 atomic units, on Base. Re-read the live 402 quote before paying.
Do I need to give GPT55 a private key?: No. Payment is signed by a buyer-owned browser wallet or local runtime. Never paste a private key into the service, a form, or a repository.
What proves delivery?: HTTP 200, the successful payment response, and the x402 receipt fields for that same request. Search visibility and quote volume are not revenue.