The purpose of the annotation, a brief descriptive and evaluative paragraph, is to inform the reader of the relevance, accuracy, and quality of the sources cited. Abstracts are the purely descriptive summaries often found at the beginning of scholarly articles or journal indexes.
For examples of scholarly annotations, please visit the Purdue OWL. Also, this link for a definition. And this link for a sample.
Summarize
Assess
Reflect
Cite
You are writing a paper about immigration laws and visa vetting
Legislator Questions San Bernadino Suspect's Visa
Annotated Bibliography Sample Entry