Alt text: Two blue glass bottles, one oval, one round with a tall neck, filled with golden liquid. The oval bottle has a blue floral painted on in darker blue and white; the round bottle features a label reading 'Bottled Sunshine', and the liquid inside is bubbly.

There are input fields for alt text in most fediverse apps, including web. Using those makes alt text much more meaningful, since they will be caught by accessibility tools like screen readers in a more functional way than when adding them in description or as comment. Just in case you don't know :)