Follow your professor's guidelines for this, but generally, this is a paragraph or two, no more.
After you complete your topic proposal, and before you begin searching the library resources for sources, you must create a Search Strategy.
Courtesy of Florida Atlantic University Libraries
Use this handy guide to help you evaluate your sources for usefulness for your topic.
Your Annotated Bibliography can be organized in three different ways:
Your professor might have a preference as to how you organize your Annotated Bibliography, but if you have a choice, the best option is usually thematically as it begins to help you make connections between your sources and provide the framework for your Literature Review and subsequent First Draft.