Penny Engine — Agent Utility APIs — Free REST and MCP tools for commerce, marketing, developer and small-business agents

Nine deterministic, no-signup API and MCP tools for real work: ecommerce profit math, pricing, subscription unit economics, cleaning bids, campaign break-even, URL cleanup, slug generation and JSON inspection. Hosted HTTPS API, OpenAPI specification, agent instructions, and examples. The free API does not require payment or personal data; a separate paid batch service is in development.