The Kubernetes API Server is at the core of the project, serving as the primary interface for not only managing clusters but also for the vast ecosystem of tools and extensions built upon it. This talk dives into the design principles that make the API server so extensible. We'll showcase SIG CLI's kubectl as an example of how the community leverages the API to create powerful user experiences. Additionally, we'll explore the recent 1.28 Sidecar KEP, illustrating how a seemingly small API modification can be challenging to implement, but can unlock significant new workload patterns.