Design-First or API-First: Where Does Future Lies?

If you are talking about API first development, you treat it as a business asset and understand the value they bring to the organization. Each API is around the contract that one can write in a description language of API like you can consider with open API for mostly reusability, broad interoperability, and consistency. If you start with API, you will allow the best plan to design the API and get feedback from stakeholders before writing any code.