Description2
Description2 is a default extension that allows you to add a description meta tag for articles automatically based on the content. This extension also adds the description to the parser output in a way that other extensions can leverage to provide the description in a different format as Extension:OpenGraphMeta does.
Custom description
You can also use a parser function {{#description2:}} to control the description displayed for the page and replace it with a custom one. You can use these parser extensions like so:
{{#description2:This is a description.}}
Things to consider
When using templates at the top of the articles, if you use <div> instead of tables for the template, be sure it doesn't render paragraphs, which otherwise will be used as the description. This may happen if you have several <div> inside the template with newlines.