x402 API Key + URL Packs: API URL Contract Linter

Overview

Validate an OpenAI-compatible base URL contract, models endpoint, chat completions path, advertised models, and sample request without calling an upstream model. Buy a $100 OpenAI-compatible API Key + URL quota pack for $11.1112 through x402, with a free readiness preview and safe delivery recovery. Start buyer evaluation at https://x402-key.558686.xyz/x402/buyer-use-cases or machine JSON https://x402-key.558686.xyz/x402/buyer-use-cases.json; checkout contract JSON is https://x402-key.558686.xyz/x402/checkout.json. Route payment activation JSON is https://x402-key.558686.xyz/x402/route/api-url-contract-linter/payment-activation.json. Browsers can inspect the quote, but payment requires a buyer-owned runtime that signs and retries the same request with X-PAYMENT. Buyers can download the route-specific first-payment client at https://x402-key.558686.xyz/x402/route/api-url-contract-linter/first-payment-client.mjs, run node first-payment-client.mjs for quote-only checks, then opt into a buyer-owned x402 payment with PAY_REAL_X402=1. Copy-ready first paid request: curl -fsSL https://x402-key.558686.xyz/x402/route/api-url-contract-linter/first-payment-client.mjs -o first-payment-client.mjs && npm install @x402/fetch @x402/core @x402/evm viem && PAY_REAL_X402=1 EVM_PRIVATE_KEY=$EVM_PRIVATE_KEY node first-payment-client.mjs. Generic clients can also discover it from the live 402 response headers: the standard Payment-Required header includes firstPaymentClient, paymentClientUrl, and sameRequestRetryRequired pointers; X-First-Payment-Client, X-Download-Install-Then-Pay-Command, and Link rel=payment-client mirror the same handoff.

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