digrart

This plugin allows you to add a meta description to each post, page, or custom post type as well as archives and taxonomies directly from the WordPress editor. Simplify SEO for your WordPress site without any extra fluff.

dig Description

Just the Meta Description. / 投稿ページやアーカイブページに、ただディスクリプションを設定できるだけのプラグインです。

CongBom

Generate most common meta tags to your WordPress site.
Open Graph (og) tag via post content and featured image:
<pre><code><meta property="og:url" content="..." />
<meta property="og:type" content="..." />
<meta property="og:title"content="..." />
<meta property="og:description" content="..." />
<meta property="og:image" content="..." />
</code></pre>
Meta description tag via post content or excerpt:
<pre><code><meta name="description" content="..." />
</code></pre>

Meta Tags Generator

It assumes that the theme's screenshot is in .png format. For smaller file size reason, I prefer using .jpg images for my theme's screenshots.

To set the record straight, .png is the preferred format, although other image formats are allowed. This is a direct quote from the Codex pages:

"Note that optionally, .jpg, .jpeg, and .gif are also valid extensions and file formats for the screenshot (though not recommended)." 

Other than that, this plugin is refreshingly small in size, and that's a good thing.

Almost there!

Automatic generate meta tags. Let your WordPress site optimize with Search engine & Social sharing.

dig Description vs Meta Tags Generator