api.21.cash provides simple address-link endpoints on the Base network that map Ethereum addresses to human-readable payment links and routing instructions (e.g., "lilpayment" or "50% to Aura Rewards"). With a small, focused surface (two endpoints), it’s optimized for lightweight integrations that need address labeling, payment routing or donation/reward splits for wallets, dApps and DeFi tooling. Requests are priced between $0.01 and $0.10, making it suitable for low-cost, high-frequency lookups.