Do I need long description?​

These questions from the Web Accessibility Initiative are helpful when deciding if you need a long description,
and what to include:

Why is this non-text content here? – Is the image decorative or is it there to convey information.

What information is it presenting? – What are the key point of information or data that this image intends
to convey?

What purpose does it fulfil? – Why is the image here? What is the context in which it is displayed, and why
is it in exactly this part of a webpage or other text content?

If I could not use the non-text content, what words would I use to convey the same function and/or
information? – How would you describe this to somebody who couldn’t see the image, but who needed to
understand the information and the context.