How to Write an Annotated Bibliography (With an Example)

To write an annotated bibliography, list your sources in your required citation style and give each one a short paragraph, the annotation, that summarizes the source, evaluates it, and explains how it fits your project. The citation comes first, formatted exactly as it would be in a reference list; the annotation, usually 100 to 200 words, comes underneath. This guide covers what the assignment actually asks for, the three parts every good annotation has, how the formats differ in APA and MLA, and a worked example entry you can copy the shape of.

What an annotated bibliography is, and why it gets assigned

An annotated bibliography is a list of sources where every entry does two jobs. It gives the full citation, the same one you would put in a reference list, and then it adds a brief commentary on the source called an annotation. That second part is what separates it from an ordinary works-cited page. A plain bibliography proves you found a source; an annotated one proves you read it and thought about it.

It gets assigned because it is excellent practice for the work that comes next. Most of the time an annotated bibliography is a milestone on the way to a longer paper or a literature review, the step where you gather your evidence and force yourself to assess each piece before you start arguing. Done honestly, it saves you from the worst version of the research paper, the one where you cite ten things you skimmed and hope nobody checks. By the time the bibliography is finished, you already know which sources are strong, which overlap, and which you will actually lean on.

The two parts of every entry

Each entry has a fixed shape. First the citation, then the annotation, in that order, every time.

The citation

This is the full reference in whatever style your assignment requires: APA, MLA, Chicago, or another. It is formatted exactly as it would appear in a reference list or works-cited page, including the hanging indent, and the entries are usually alphabetized by the author's last name. Nothing about the citation changes because it lives in an annotated bibliography. If you can format a reference list, you can format this part.

The annotation

The annotation is the paragraph underneath the citation, and it is where the real work happens. A complete annotation does three things, which is the framework most university writing centers and library guides use. It summarizes the source, telling the reader what it argues and what it found. It evaluates the source, judging its credibility, method, or usefulness. And it reflects on relevance, explaining how this particular source fits into your own project. Hit all three and the annotation is doing its job; skip the last two and you have written a summary, not an annotation.

How long an annotation should be, and the common types

Most annotations are about a paragraph, somewhere in the range of 100 to 200 words, unless your instructor sets a specific length. That is enough room to summarize, evaluate, and connect a source without padding. If your assignment is silent on length, that range is a safe default, and a few sentences each is normal.

The length depends on the type you are asked to write, and there are two common ones.

Descriptive (summary) annotations describe what the source is about and nothing more: its argument, scope, and main findings. They can be shorter because they only summarize. You will see these when the goal is just to map a field quickly.

Critical (evaluative) annotations do everything a descriptive one does and then assess the source, commenting on its reliability, method, bias, or limitations, and saying how it serves your paper. These run longer and are what most college assignments mean when they say "annotated bibliography," because the point is to show you can evaluate sources, not just describe them. If you are unsure which one your assignment wants, ask, because the length and the depth both follow from that answer. The format conventions are well documented in the Purdue OWL's annotated bibliography guide, which is a reliable reference for the structure of each entry.

A worked example entry

Here is what a single critical entry looks like in APA style. The source below is a real, peer-reviewed paper, and the citation is formatted exactly as an APA reference would be, with the annotation hitting all three parts.

Read that annotation against the three parts. The first sentences summarize the study and what it found. The middle sentences evaluate it, noting the peer review and the design limits in the same breath. The last sentence reflects on relevance, saying exactly how the source serves the writer's argument and how its weakness will be handled. That last move, naming the gap and how you will cover it, is what turns a description into an evaluation a grader rewards.

How to write one, step by step

1. Find and actually read real sources

An annotated bibliography is impossible to fake well, because each annotation has to evaluate a source you understand. Start by gathering sources that genuinely fit your question, then read them, not just the abstract. This is also where the most common shortcut goes wrong: asking a chatbot for a ready-made list of sources, which it will invent confidently. Build the list from real searches instead. If you need a method for finding and judging sources, our guides on finding sources for a research paper and finding credible sources walk through the whole workflow.

2. Cite each source correctly

Format every citation in your required style and alphabetize the list by author surname. Get this right first, because the annotation is easier to write once the source is properly identified, and a sloppy citation is the fastest way to lose easy marks. Double-check the details against the actual source, not against a citation generator's guess.

3. Write the three-part annotation

For each source, write the paragraph in three moves. Summarize the argument and findings in a sentence or two. Evaluate the source, who wrote it, how solid the method is, what it does and does not support. Then state its relevance, the specific reason it earns a place in your project. Keep it to a paragraph, write it in your own words, and avoid quoting; the point is to show you have digested the source, not to copy from it.

APA versus MLA, briefly

The two parts stay the same in every style; only the formatting details shift. In APA, the page is usually titled "Annotated Bibliography," references are alphabetized with a hanging indent, and the annotation begins on a new line, indented as a block beneath its citation. APA citations put the year right after the author and use sentence case for titles.

In MLA, the list is titled "Annotated Bibliography" or "Works Cited," entries also use a hanging indent, and the annotation follows on the next line, indented to align under the entry. MLA citations omit the standalone year that APA leads with and use title case. The differences are cosmetic next to the annotation itself, which reads the same regardless of style. Whatever the style, check your instructor's specific requirements, since some ask for a particular annotation type or length that overrides the defaults.

Where CiteOwl fits

The hard part of an annotated bibliography is not the formatting, it is writing an accurate summary and a fair evaluation of a source you have genuinely read. That is the part general chatbots get wrong, because they will summarize a paper from a plausible guess and sometimes the paper does not exist at all. CiteOwl works the other way around: it is verify-first, so it searches for and reads the real paper before it writes anything about it, and it attaches the supporting quote it relied on. That means it can help you draft a summary-and-evaluation annotation that is grounded in the actual source rather than a hallucinated one. You still decide the relevance, since only you know your argument, and you still own the final words. CiteOwl just makes sure the summary describes a paper that is really there and really says what your annotation claims.