website/layouts/partials/head_meta_seo.html

<meta name="author" content="{{ .Site.Params.Author }}" />
{{ if .IsPage }}
    {{ if .Params.tags }}
        <meta name="keywords" content='{{ delimit (sort .Params.tags) ", "}}' />
    {{ end }}
    {{ if .Params.description }}
        <meta name="description" content="{{ .Params.description }}" />
    {{ else }}
        <meta name="description" content="{{ substr .Summary 20 }}" />
    {{ end }}
{{ else }}
    {{ if .Site.Params.description }}
        <meta name="description" content="{{ .Site.Params.description }}" />
    {{ end }}
{{ end }}