Design-first is a methodology for delivering APIs that begins with defining an OpenAPI specification, documenting, and mocking the API. This allows teams to iterate on the design with stakeholders before any code is written. A design-first approach to delivering HTTP APIs is often considered more efficient than writing and iterating on code directly.
While the design-first methodology can appeal to some teams and works well when there is buy-in, not all teams may be ready for this approach. Some teams may require additional training and experience before adopting it effectively. It is common to support both design-first and code-first approaches to delivering APIs, allowing organizations to establish a balance that suits different team needs and workflows.