A Phil Arena blog post with links led me to this nice ISA discussion of abstracts, which are important but too often botched. A few years I wrote my own brief rant on the topic based on my own experience with a class assignment requiring students to analyze academic articles. They are too long, too rambling, too unclear, etc. to the point of uselessness (or making the reader annoyed).
Even in the ISA discussion, one of the people includes their own abstract, which I would classify as too long (it is 183 words) and therefore would not use as a model. In 100 or so words you should have presentation of topic, hypothesis/argument, methods, conclusion/implications. Here's what I wrote back then:
All abstracts should state the main argument front and center, then the basic data/methods used, and the conclusion(s). Not only do you not need a lot of detail, you should avoid it. I've read abstracts that are something like 200 words, or two dense paragraphs. A Google search reveals many university links about how to write abstracts (such as my alma mater) advocating for 200 word abstracts, but that is not the norm for articles and in my opinion is too long. American Political Science Review, for example, limits them to 150 words.
Funny how tough this very basic task is, though I've mucked it up plenty myself by seeing it as this last hurdle before I can get the article manuscript submitted. This is one case where teaching actually forced me to think differently about my research.