`description.exists`

Default: error
Plugin: description

A page has a <meta name="description"> tag.

Why: Search engines often show the description below the title. Without one, they pick a piece of the page text, which may not describe the page well.

When off: pages without a description pass.

<!-- ✗ Fails -->
<head>
  <title>About us</title>
</head>

<!-- ✓ Passes -->
<head>
  <meta
    name="description"
    content="Who we are, and how we bake our bread every morning."
  />
</head>

References

Google: Snippets: Google recommends a description at least for important pages, and uses it for snippets.
Google: SEO Starter Guide: A good description is short, unique, and relevant.