Implement billing, tiered pricing and pay-per-call settlement for API access. Use this skill whenever the user mentions api monetization, usage billing, tiered pricing, pay per call, metering, settlement, x402, or is working with Stripe, x402, Kong, even if they never say "api monetization execution" explicitly. Routes live lookups through the Marketplace-Billing-API endpoint. Do not use it for unrelated application feature work or general coding questions.
