How to Write an Annotated Bibliography in APA, MLA and Chicago

An annotated bibliography is a reference list in which every entry is followed by a short paragraph of your own, usually 100–200 words, saying what the source contains, how sound it is, and what you intend to do with it. The citation part follows ordinary APA, MLA or Chicago rules. What changes between the three styles is narrow, covering where the annotation sits, how far it is indented, and how the page is spaced. The formatting takes a minute to learn; the paragraph is the part that takes work.

This guide covers the format for all three styles with a worked example, then the difference between an annotation that describes a source and one that assesses it.

What an annotation is supposed to do

A usable annotation does three jobs in one paragraph. It summarises the argument, it says something about quality or scope, and it connects the source to your own project. Skip the third job and you have written a book blurb.

Tolonda Henderson makes a related point about how these assignments go wrong. Prompts often tell students how many sources to include without saying anything about how many to consult along the way, which suggests to a novice researcher that the first five items clearing the basic criteria will do (Henderson, 2024, p. 3). Her counter-assignment, the "Unbibliography", asks students to list ten sources they considered for their annotated bibliography and rejected, annotating why each was considered and why it was dropped (p. 8). Discarding a source that initially looked promising is part of the research process rather than wasted effort (p. 4). Annotated bibliographies are usually set to start the research for a larger project, so treat each annotation as the record of a decision you have already made about the source.

Weak (describes only):

This article discusses citation practices in scientific writing. It covers citation styles, reference management software and problems with citations.

Stronger (describes, assesses, connects):

A short review aimed at medical authors, covering citation systems, reference managers and common citation errors. The evidence is compiled rather than original, so it is better used for framing than for statistics. Useful to my chapter 2 for its account of how bibliographic errors damage a manuscript's credibility (p. 99), and for the finding that citation problems contribute to 10–15% of rejections (p. 100).

The second version shows a supervisor which parts of the source you actually used, and where.

APA 7 format

Entries are formatted and alphabetised exactly as in a normal APA reference list, double-spaced, with no extra blank line between them.

The annotation begins on a new line beneath the entry. Indent the whole annotation 0.5 inches, lining it up with the hanging indent of the reference above, and do not add a further first-line indent. If an annotation runs to more than one paragraph, the later paragraphs take an additional 0.5-inch first-line indent.

MacEwan University Library. (2024). Chicago notes-bibliography documentation
     style guide. https://library.macewan.ca/sites/default/files/pdfs/
     chicago-notes-bibliography.pdf

     A library and writing-centre guide to the notes-bibliography system,
     updated for the 18th edition of the manual. Practical rather than
     scholarly: it works through quotations, paraphrase and note formatting
     with side-by-side examples. I am using it as the formatting authority
     for the Chicago entries in this paper, and for its warning that
     patchwriting counts as plagiarism even when the source is cited (p. 6).

MLA 9 format

The entry itself is formatted as a Works Cited entry. The annotation goes on a new line below it, indented one inch from the start of the entry, which keeps it visually distinct from the half-inch hanging indent used by entries running over one line. Extra paragraphs are indented too, with no blank line between them. Title the page "Annotated Bibliography" or "Annotated List of Works Cited".

MacEwan University Library. Chicago Notes-Bibliography Documentation Style
     Guide. MacEwan University, 2024, library.macewan.ca/sites/default/
     files/pdfs/chicago-notes-bibliography.pdf.

          A library and writing-centre guide to the notes-bibliography
          system, updated for the 18th edition of the manual...

Chicago format

Chicago annotated bibliographies use ordinary bibliography entries, alphabetised by author surname, with a hanging indent and single spacing. The annotation follows on a new line, indented half an inch, and new paragraphs inside it take the same half-inch indent.

MacEwan University Library. Chicago Notes-Bibliography Documentation Style
     Guide. MacEwan University, 2024. https://library.macewan.ca/sites/
     default/files/pdfs/chicago-notes-bibliography.pdf.

     A library and writing-centre guide to the notes-bibliography system...

Chicago has two documentation methods, notes-bibliography and author-date, and which one you use is set by your discipline or your instructor. If you are still choosing, our guide on which citation style to use covers the decision; for APA entry formats specifically, see how to cite a book, an article and a web page in APA 7.

Check the entries before you annotate them

An annotated bibliography puts your sources under a brighter light than a plain reference list does, because each entry now carries a claim that you read it. That makes a wrong author name, or a source that does not exist at all, more expensive than usual.

Subramanian and colleagues catalogue what goes wrong. Incorrect author names, titles and publication details are common, and they undermine the credibility of the work they appear in (Subramanian et al., 2025, p. 99). The same review reports that citation-related problems are a contributing factor in 10 to 15% of manuscript rejections (p. 100).

Two habits push the error rate up. The first is trusting a reference manager to act as a verifier. Jin and colleagues note that market-leading tools were built to organise, store and format references rather than to confirm they are real, and that EndNote's "Find Full Text" retrieves the full text of a reference you already have without checking whether its metadata correspond to an actual publication (Jin et al., 2026, p. 5).

The second is asking a chatbot for sources. Szeider, reviewing the evidence on fabricated citations, cites tests in which error rates ran above 70% for earlier models, and fabrication rates above 80% for certain publication categories, complete with invented author names, venues and DOIs (Szeider, 2025, p. 2). Entries like those are formatted correctly and fall apart as soon as someone follows the link.

The practical fix is dull and quick. Before you write a single annotation, open each source and confirm four things against the article itself: the author list, the year, the exact title, and the page range you plan to quote. If you cannot open it, do not annotate it.

If you would rather not retype the entries by hand, cytado's bibliography generator builds the list from real records in Crossref, OpenAlex, DOAJ and Biblioteka Nauki, and the citation generator formats single entries in APA, MLA and Chicago. There is also a walkthrough of the annotated bibliography generator if you want the summaries drafted from the source text rather than from a model's memory. The academic sources cited in this article were found the same way.

Before you hand it in

Five checks, in order:

1. Every entry opens. Click each DOI or link.
2. Author surnames, year and title match the source itself, not your notes.
3. Each annotation says something evaluative, not just descriptive.
4. Each annotation names a use: which chapter, section or argument it serves.
5. The list is alphabetised, and the indentation follows one style throughout.

The first two take about ten minutes for a twenty-item list, and they catch the errors a supervisor's spot-check would find.