How to ask AI for useful, accessible image descriptions
To request useful image descriptions from AI, state where the image appears and what it needs to communicate. The best description depends on its role on that page rather than only the objects it contains.
AI can help prepare a draft, but you need to check the image and context. This process distinguishes three deliverables often mixed together: alternative text, captions and longer explanations.
1. Explain how the image will be used
State whether it illustrates a concept, presents data or functions as a button. Also provide nearby text when needed to understand its role.
The W3C alt decision tree organizes choices according to that role. It is a reference for deciding whether the alternative should communicate information, an action or remain empty.
2. Choose the description type
A caption contextualizes the image for people reading the page. Alternative text replaces necessary visual information, while a longer explanation can describe relationships that do not fit into one sentence.
| Situation | Delivery to consider |
|---|---|
| Photograph adding information | Brief alternative tied to context |
| Purely decorative image | Empty alternative in the appropriate implementation |
| Chart with several relationships | Summary and explanation of data in the content |
| Icon used as a link | Description of the action or destination |
Do not choose the type solely by image size. A small figure may carry information essential to completing a task.
3. Request a draft with clear limits
Imagine a photograph of a desk with a closed laptop and a task notebook, used in an article about planning the week.
Analyze this image in an article about weekly planning.
First, state what visual information it adds to the text below.
Propose brief alternative text and a separate caption.
Do not infer identity, intention or emotion without image evidence.
If there is no relevant additional information, explain why
it could be treated as decorative in this context.If the tool cannot analyze the image clearly, ask it to identify that limitation. A confident description does not prove the details were recognized correctly.
4. Check what was observed
Compare each part of the description against the image. Remove objects, relationships and characteristics the response invented or that are irrelevant to the page.
The W3C informative image guidance emphasizes conveying the necessary meaning. That helps avoid an inventory of objects that does not explain why the image is there.
5. Review alongside nearby text
Read the paragraph, suggested alternative and caption in sequence. Check whether essential information is missing or the same sentence is being repeated without benefit.
For charts, verify numbers and relationships against the data source. AI should not turn a visual impression into a statistical conclusion you have not checked.
6. Keep the context decision
Record why the alternative was chosen and review it if the image moves. The same photograph may serve a different purpose on another page.
If you also produce the illustration, the image generation brief guide helps define its role before creation.
Frequently asked questions
Are alternative text and captions the same thing?
No. Alternative text replaces visual information according to context; a caption appears for everyone and can add explanation.
Does every image need a long description?
No. The image purpose and information guide the choice. Decorative images may have empty alternatives; charts may need additional explanation.
Can I publish AI-suggested alternative text immediately?
Review it first. Check what actually appears and whether the description communicates the necessary information in that context without invented inferences.