What is an API-First?

Under an API-first approach, the team designs the contract (endpoints, data shapes, auth model) as a first-class artifact, often writing an OpenAPI spec before a line of implementation code exists. Frontends, mobile apps, and third-party integrations all then consume that same well-defined contract, rather than the API being an afterthought reverse-engineered from whatever the web UI happened to need internally. The payoff is consistency and reuse: if the API is genuinely designed first, a mobile app, a partner integration, and an internal admin tool can all build on the identical, stable surface instead of each needing custom backend support. It also forces earlier thinking about versioning, error handling, and edge cases, because the API can't quietly hide behind a specific UI's assumptions. The API-first approach is especially valuable for platforms meant to be extended by others — if third parties are expected to integrate, a deliberately designed, documented, stable API isn't optional, it's the actual product surface everything else builds on top of.