Design functions, modules, CLIs, REST/RPC APIs, and data contracts that are easy to use correctly and hard to misuse. Auto-load when designing or reviewing any public interface — function signatures, module boundaries, CLI commands and flags, HTTP/RPC endpoints, event schemas, or data contracts; when evolving an existing API without breaking consumers; when designing error responses; or when deciding versioning strategy. NOT for whole-system architecture (system-design), NOT for analyzing existing seams (architecture-analysis), and NOT for LLM output contracts (llm-integration-reliability).
