The meta description tag has no DIRECT SEO value, whether you add one or not will have no impact on the actual position a webpage ranks. Since they have no direct SEO benefit there’s nothing to be gained from keyword stuffing them!
Example description meta tag:
<meta name="description" content="Meta tags hold little value to SEO per se, in fact as #Google's latest algorithms include PageSpeed as a ranking factor adding code like the keywords meta tag is #SEO damaging!" />
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