Buy a tiered prepaid API key with USDC, USDT, or BTC (no auth required)

Email-based tiered key purchase: send the tier-specific amount in USDC/USDT/BTC to the platform wallet (EVM USDC/USDT: 0xAd982CB19aCCa2923Df8F687C0614a7700255a23 — same on all chains; Solana USDC/USDT: 6a1mLjefhvSJX1sEX8PTnionbE9DqoYjU6F6bNkT4Ydr; Bitcoin BTC: bc1qg7qnerdhlmdn899zemtez5tcx2a2snc0dt9dt0), then call this endpoint with the transaction hash, your email, and the tier you paid for. Returns an API key valid for 30 days at the tier's daily limit and credit allocation. Fixed pricing: Pro = $29 (10000 requests/day, 1,000 attest credits), Enterprise = $99 (100000 requests/day, 5,000 attest credits), the same allocation as the card subscription (POST /v1/keys/checkout). One-month prepaid; to renew, call this endpoint again with a new payment. For pay-what-you-want credit purchases without a fixed tier or expiry, see POST /v1/keys/buy (wallet-native, agent-friendly). Crypto sent on unsupported chains cannot be recovered. All purchases are final and non-refundable. Tron is NOT supported on this endpoint (only EVM, Solana, Bitcoin). Response envelope note: this endpoint stands apart from the main router and returns a flat {success, key, ...} object — NOT the {ok, data, meta} envelope used by the main /v1/* router. Its error responses (400, 405, 409, 422) are likewise flat {"error": "..."} objects, matching POST /v1/keys/create.