”The quality of your snippet — the short text preview we display for each web result — can have a direct impact on the chances of your site being clicked (i.e. the amount of traffic Google sends your way). We use a number of strategies for selecting snippets, and you can control one of them by writing an informative meta description for each URL.”
Raj Krishnan, Google: Improve snippets with a meta description makeover (2007)

”Like your HTML page title, your meta description tag should be custom-written for each landing page to match its specific content.”
Jennifer Grappone & Gradiva Couzin: Search Engine Optimization (2006), s. 154