At least one of your sources for your annotated bibliography needs to be empirical.
Empirical studies conduct original, observational or measurement-based research, rather than discussing a theory or belief. So, you will want to look for articles that are conducting this type of research. To identify an empirical study, look for papers with a methodology and/or results section. Empirical studies should also typically include the specific research question being studied and an explanation of the population or phenomena being investigated.
The video below walks through the steps of identifying an empirical article:
Video credit: USU Libraries