On r/UXDesign and r/UI_Design, "how do you hand off animations?" is a recurring thread. The common pain is that developers receive a nice video and guess the numbers.
What a good motion spec contains
For each transition: what triggers it (tap, hover, data loaded), which elements change, which properties (position, scale, opacity, colour), the duration, the easing curve (as cubic-bezier values) or spring settings (stiffness, damping, mass), delays and stagger, and what happens on interruption.
Use shared names
Name states the way the code does: idle, loading, success, error. Name inputs as the data they represent: isLoading, progress, onSuccess. This avoids a translation step.
Motion tokens
If your product reuses the same timings, store them as tokens such as duration-fast: 150ms, ease-standard: cubic-bezier(0.2, 0, 0, 1). Developers reference tokens instead of copying numbers.
Ship the file instead
For complex, multi-state motion, the cleanest handoff is no rebuild at all. Lottie hands off a played animation. Rive and ExodeUI hand off an interactive file with a state machine that developers drive with inputs. ExodeUI files are readable JSON, so developers can review changes in git. We make ExodeUI.
Review together
Check the implementation side by side with the design on a real device. Small easing differences are easy to miss in a browser on a fast laptop.