I think there was a thread here on MSG in which it was stated that the SS search is now based heavily on descriptions, and it's worth revisiting your portfolio on SS and editing the descriptions so they consist mainly of the most important keywords.

Is that true?

There was a technical problem some weeks ago - and again in the last few days - resulting in some pictures NOT being found at all through keywords.

When that happens, description is paramount being the only thing being searched.

In normal conditions, I don't know but it may be worth paying attention to description anyway.
External search engines may like descriptions more than kewwords too.