sceneAuthoring.reviewState

The read of the review the rest of this toolbox writes. changes opens a review, acceptChanges and rejectChanges consume one and refuse when none is open — this reports whether one is open and how much is in it, so a script picks the call to make instead of learning the ordering by being refused.

local s = tools.use("sceneAuthoring", "reviewState")
if not s.open then
    tools.use("sceneAuthoring", "changes")
end
tools.use("sceneAuthoring", "acceptChanges", "edits")

Returns { open, added, updated, removed, edits, total, scene }. With no review open, open is false and every count is zero — which is also the answer after a review is fully accepted or rejected, since consuming one closes it.