The graveyard of design systems is full of beautiful Figma libraries that no engineer ever used. The problem is almost always the same: the system lived in design, and code drifted away from it.
Tokens are the contract. Color, spacing, and typography should be defined once and consumed identically by design tools and code. When they share a source of truth, drift becomes impossible.
Components map one-to-one. Every component in the design library should correspond to a real, production component — same name, same props, same states.
Treat the system as a product. It needs an owner, a roadmap, and real users — your own teams. The systems that thrive are the ones treated with that seriousness.