APIs are the contracts between systems. Break them carelessly and you break the systems that depend on them. Design them well and they become an asset that accelerates every team that consumes them. Here are the principles we apply on every API project.
Design for the Consumer First
The most natural starting point when building an API is to model your database and expose it. This is almost always wrong. Your API consumers — whether internal front ends, mobile apps, or third-party integrations — have specific needs that often don't map neatly to your storage model. Start with the consumer's use cases and work backwards to the data layer.
Version from Day One
The most common API regret we hear from clients is not versioning from the start. "We'll add it later" is a lie you tell yourself. Add /v1/ to your path from the first endpoint, even if you never release a v2. The discipline it enforces — thinking about what breaking changes look like, planning for evolution — is worth the few extra keystrokes.
Be Consistent, Then Be Correct
Inconsistency is the silent killer of developer experience. If most endpoints return snake_case but a few return camelCase, if some use id and others use uuid, if errors come back in three different shapes — consumers have to write defensive code everywhere. Pick conventions and apply them without exception. An API style guide is not optional on any project we deliver.
Treat Errors as First-Class Citizens
Error responses are used in every unhappy path — which in production is a significant percentage of all requests. Design your error contract with as much care as your success contract. We follow RFC 9457 (Problem Details for HTTP APIs): machine-readable error codes, human-readable messages, and a consistent JSON envelope that client developers can rely on.
Document It Before You Build It
OpenAPI (Swagger) specifications written before implementation serve as a forcing function. They surface ambiguities, drive alignment between front end and back end teams, and produce living documentation that never drifts from the implementation when you use contract-first tooling. We treat the OpenAPI spec as the source of truth, not an afterthought.
