Good alt text is short and factual
It describes what matters in the image, not how beautiful it is. Screen reader users want the content, not the adjectives.
It is also an SEO signal
Search engines read alt text to understand images. Missing alt text is one of the most common accessibility failures on the web.
Two credits means you can do the whole site
At this rate, running every image in a library is affordable. That is the difference between fixing accessibility and planning to fix it.
FAQ
How long should alt text be?
Usually one sentence. Complex charts need a longer description in the page body instead.
Does it work for decorative images?
Decorative images should have empty alt text. Skip them rather than describing them.
Can it read text inside the image?
It summarises visible text. For full extraction use the OCR tool.