animation.observe

What the engine is posing right now, one line per body.

tools.use("animation", "observe")          -- every body in the scene
tools.use("animation", "observe", "hero")  -- one character

Each entry carries:

• animating — the engine's own verdict, read off the pose it measured landing on the armature rather than off any component field.
• reason — why a still body is still: deactivated, noRiggedSkeleton, noGraph, clipUnreadable, noOutputNode, retargetPending, retargetMatchedNoRoles, stopped, finished, paused, poseNotApplied, poseUnchanged.
• clip, time, duration — the clip driving it and where its playhead is.
• matched of total — how many of the body's bones that clip reaches. A clip from an unrelated rig reads 0 of 50 while its playhead advances.
• bonesWritten, poseRevision, sinceChangedMs — the engine's measurement: how much of the pose landed, how many times its values changed, and how long ago they last did.

animation.observe() in Luau returns the full observation this condenses, and /zero/runtime/animation serves the same document as a file.