Interaction specifications that give development the information needed to implement behaviour correctly, not just visual states, but the triggers, transitions, and logic that connect them. Animation specifications include: duration (150ms for micro-interactions like button press feedback, 250-300ms for panel reveals and modal entrances, 400ms for page-level transitions), easing curves (ease-out for elements entering the screen, fast start, slow end; ease-in for elements leaving; ease-in-out for elements moving within the screen), and the specific property being animated (opacity + translateY for toasts; scale + opacity for tooltips; height or max-height for accordions). Figma Smart Animate prototypes demonstrate timing and easing before development begins, removing interpretation ambiguity. Complex interaction specifications for drag-and-drop (ghost element on drag start, drop target highlight, reorder animation), inline editing (click-to-edit pattern with cancel/save affordances, keyboard shortcuts, focus management), multi-step wizard flows (progress indicator, back/forward navigation, validation gating on step advance), and data tables (column sort, row selection, bulk actions, pagination). Loading skeleton screens specified as components rather than spinners, shaped to match the content they replace so layout shift is minimised when data loads.