d tags for human-readable title are not a good idea as you can't change it
I use it as a nicer-to-have URL, because then you can do domain/<nip05>/d-tag, but, since you can't change the d tag it's better to keep a title tag with the human-readable/editable value
I think 30040s should follow NIP-23's format as closely as possible to avoid having a bunch of differently-named tags that mean the same thing
"title", for the article title
"image", for a URL pointing to an image to be shown along with the title
"summary", for the article summary
"published_at", for the timestamp in unix seconds (stringified) of the first time the article was published