With alt txt / alt text / Descriptions, don't just repeat the accompanying text. Sight-impaired people can already get that from the accompanying text.
Add detail if possible. Describe why you're using that image. Provide missing context.
You can think of #AltText as additional word count to provide deeper, richer experiences.
So, not just "A black bird" but "A large crow with opened wings on a tree stump in Fall in Maine. It is calling loudly"