U answered well but left most important point which refers to Character Limit.

@”Describe the page content accurately and concisely while staying within the 160 character limit.”

I would like to add some here, that no search engine confesses about the character limit in Title and Meta Tags.

In my case my website is still in search for upto 300 characters in Description Tag (bold tags upto 300 characters).

Meta Description is for a snippet for your particular page. You can write short keyword rich description or some snippets with your keywords and just see the wonders.

I am not telling here that there should not any character limit and you should exploit the Meta Description Tag but to describe your page in a vary short and decent manner with out too much keyword stuffing and very long paragraphs.

RM