I've been answering a lot of questions about having enough content in your product descriptions recently and thought it would be nice to share some ideas with you.
Google likes to see a fair amount of unique content on every page. That usually means 300 - 500 words.
I've found Shopify stores can make due with a bit less, but the more content you have the better and faster results will be.
Aim for at least 200 - 300 words or a handful of paragraphs.
You might also find that this additional content helps your conversion rates and SEO ranking too, which are nice extra benefits.
Google wants to see content on every page but realistically your homepage, product pages, and collection pages are the important ones (in that order). If you use the blog or have helpful Shopify Pages, those are also important and would be as important as the collection pages.
Another great optimization for your store is to make sure your product's structured data is setup correctly for Google's Rich Snippets. With those you'll get more traffic and better converting traffic.
You can either audit your store's structured data by hand or install JSON-LD for SEO and have all the structured data you need.
It's already helping over two thousand Shopify stores with their structured data and it could help you too.