Essentially, the descriptive abstract only describes the work being summarized.
A good informative abstract acts as a surrogate for the work itself.
That is, the researcher presents and explains all the main arguments and the important results and evidence in the paper.
A good strategy to begin composing your abstract is to take whole sentences or key phrases from each section of the paper and put them in a sequence that summarizes the contents. University of North Carolina; Borko, Harold and Seymour Chatman. University of Wisconsin, Madison; Hartley, James and Lucy Betts. Writing Tutorial Services, Center for Innovative Teaching and Learning. Citing to just a journal article's abstract does not confirm for the reader that you have conducted a thorough or reliable review of the literature.
Then revise or add connecting phrases or words to make the narrative flow clearly and smoothly. "Criteria for Acceptable Abstracts: A Survey of Abstracters' Instructions." 14 (April 1963): 149-160; Abstracts. "Common Weaknesses in Traditional Abstracts in hte Social Sciences." 115 (January 2015 ): 41-47; Writing Report Abstracts. If the full-text is not available, go to the USC Libraries main page and enter the title of the article [NOT the title of the journal].