Primerpedia is a proof-of-concept demo for the Concise Wikipedia proposal. It provides short summaries of Wikipedia articles, for when you just need a quick overview at the topic.
Try the live demo here: https://tools.wmflabs.org/primerpedia
To achieve this, it uses the MediaWiki API to fetch the first section of an article, and cleans it up for presentation, removing extra details and editing-related templates (currently using the cleanup procedure implemented by the MobileFrontend extension).
This tool should also help identify issues with the lead sections of Wikipedia articles, which, according to the Manual of Style, "should define the topic and summarize the body of the article with appropriate weight."