AACs are broad accessibility criteria applied when user stories are created. Instead of developer-focused, they’re BA-focused. And describe key behaviours the finished feature needs to display – an outcome, but they don’t go so far as in specifying how to do it.
Instead, they act as guard rails allowing a developer to implement the feature in any possible way, if the outcome is met.
They define the boundaries of a user story and are used to confirm when a story is complete and working as intended. They're written in plain language and easily understood by members of a team who have different expertise and varying levels of fluency in each other’s technical jargon.
Read the blog post: How Australian supermarket Coles creates accessible user stories
The AACs developed by the Coles Accessibility Team were inspired by the UK Government's Government Digital Service (GDS) work detailed in the blog post Improving accessibility with accessibility acceptance criteria.
The Accessibility Acceptance Criteria are kindly shared by Mel O'Brien publicly through her GitHub repository, the original IP belongs to Coles.