API Design & Developer Experience

Principles for designing TypeScript library APIs and evaluating developer experience.

Goal: APIs should feel obvious, fast, safe, and composable — with great defaults and great escape hatches.

Quick Reference

Foundational

• Emergent extensibility — Best extension points look like well-designed APIs, not plugin systems
• Composition over configuration — devtools(persist(fn)) beats { middlewares: [] }
• Onion model — Transformative middleware innermost, observational outermost

API Surface