Explanation in layman terms

Imagine you are part of a team building a new house. You have plumbers, electricians, carpenters, and the client who will live in it. What's the very first thing you do? You don't just start laying bricks and hope for the best.

First, an architect creates a detailed blueprint. This blueprint is the single source of truth. It defines:

• The exact dimensions of every room (the response structure).
• Where every door and window is located (the endpoint paths).
• Where the electrical outlets and water pipes will go (the request/response fields).

Everyone involved--the client, the construction crew, the plumbers, the electricians--must review and sign off on this blueprint before any work begins.

The API Contract is the blueprint for your software. By getting everyone to agree on it first, you ensure that the frontend team (designing the furniture), the backend team (building the house), and any other connected services (the utility companies) are all working from the same plan. This prevents disastrous situations, like building a beautiful kitchen only to find out the plumbing was planned for the wrong wall.

Gain Deeper Understanding

Actions	What you'll learn
Listen to this Podcast with James Higginbotham from 8:22 mins to 13:13mins	How API design facilitates communication between different stakeholders
Watch this talk from Joshua Bloch from 2:02 mins to 3:26 mins	The role an API plays in a software and why the design matters.
Read the article "Understanding the API-First Approach to Building Products" by Janet Wagner	How agreeing on an API contract enables parallel development and reduces the risk of failure in design.
Read the section "Comparing Design-first and Code-first" in the article	Why prioritizing design before implementation, a counter-intuitive concept, leads to a shorter delivery cycle than a code-first approach.

Put it into practice?