API and Interface Design

Overview

Design APIs and module boundaries with contract-first thinking. Apply Hyrum's Law (all observable behaviors will be depended on), the One-Version Rule (prefer one way to do something), and clear error semantics. Public interfaces deserve more care than internal ones.

When to Use

• Designing REST or GraphQL API endpoints
• Creating module boundaries within an application
• Building SDKs, libraries, or shared packages
• Defining function signatures that cross module boundaries

Core Principles

Contract-First Design