Ranked by AI agent readiness across MCP, API, CLI, Skills, and Docs.
Payments with remote MCP (25 tools), REST API with OpenAPI, mature CLI, progressive-disclosure SKILL.md, agent toolkit SDKs, and Agentic Commerce Protocol
Developer billing with remote MCP (Speakeasy-generated), full REST API with 4 SDKs and OpenAPI, CLI for webhooks, llms.txt, but no agent skills