How To Create Dynamic WordPress Tags

[MyNet]

Does anyone know how to make WordPress "tag" pages automatically generate a description based on the posts included in the tag?  I have a lot of tags, and most of them rank well for long tail keywords.  However I have noticed that although they have a dynamically generated "title meta tag" they do not generate a "description meta tag".  I know WordPress lets you customize the description for each tag, but I have way to many for that.  I need the description meta to be auto generated from the posts that are being tagged, rather than not including one at all.

Does anyone know how to do this?

[Vahe.Arabian]

MyNet, I would encourage you to actually write unique meta descriptions as to some extent it can determine you sites ctr.