4.3 Success Criteria   ?These prompts should occur before [what would
be so prescient as to anticipate the author's intent?]
I expect you mean the author's trying to initiate use of a feature that has
accessibility consequence, such as insert image add alt="...",
or create table -- add summary.

Such examples might clarify your meaning.

For some "at the time " seems more likely to be following what the author has
done, at which time the accessibility consequences can be determined.