Entry point to the x402 Carbon Retirement API on Base. Returns every endpoint you need plus a live snapshot of the top 3 carbon classes and marketplace listings by liquidity. Discover, quote and certificate are free. Retiring is paid: each retirement costs the credit price plus a fee, sent from your own wallet (prepare/retire) or relayed from a signed USDC authorization (prepare-auth + POST actions/retire). Full spec at /openapi.json.