Google's John Mueller said on Twitter that it is best not to leave your meta descriptions blank. Instead he said try to fill them out because you know your content best.
This is despite a recent study from Yoast that shows that Google often uses your web site content, not your meta description, for your Google search result snippets.
Here are the tweets:
I'd generally recommend specifying one, you know your content best.
— 🍌 John 🍌 (@JohnMu) October 29, 2018
Now, while you are writing the content, I do recommend you fill in your meta descriptions. If Google doesn't use it, so be it. Your CMS can also auto-generate useful meta descriptions based on the content you enter into your CMS. In either case, I wouldn't intentionally leave them blank if you have time and resources to enter them.
But I also wouldn't count on Google always using your meta descriptions for the snippets over what Google thinks is best. Because really, who knows your content best? You or Google? :)
Forum discussion at Twitter.
