Ooh, I always want the authours tagged if possible! Mostly because if a tagged authour I follow reblogs it, I get to see other authours that the reader considers similar enough to rec together with this person I love!
Since I love Gen recs, it’s usually about a single character, instead of a ship, or about a bunch of fic with a similar tone. (Agree it should all be one fandom, unless you’re dealing with fandoms that have a huge overlap of fans.) Lists with similar tones are actually my favourites. “Ten fic with haunting prose”, “my favourite dramatic fic about siblings from 2025”, “dark-ish fic with hopeful endings”, etc.
I like a brief summary/teaser (usually a sentence or less) and then some of the reasons the reccer enjoyed it. The goal is to interest the reader just enough that they click through and read the actual fic’s summary and tags, not tell them everything they need to know.
I often include warnings in my own recs, but rarely ratings, since I find that information about tone and major warnings will usually provide more information. It doesn’t have to be the usual AO3 warnings either - I used to target my recs at aroace fans, so I’d include the amount of icky kissing in the warnings section.
If you’re going to include a wide range of ratings, people often start with the lighter ones and end with the higher ratings. They also often separate Gen and shippy stuff if they’re including both.
But the absolutely best thing you can include is bias! The more I learn about what you like and dislike, the more valuable your recs become. Praise fic for being canon compliant, or having great worldbuilding, or for the writing style, or how steamy the sex is - things that show me how you’re judging what’s on the list. I’ve followed several people because they cared about elements of fic I also cared about, to the point that I could trust their recs without even having to read the blurb.
Basically, I think your recs should focus on the elements you care about, because those are the things where your opinion will actually tell us something. I don’t include ratings, because I have nothing to say about them that the fic doesn’t say better. I do include information about how many times I needed to take a break and calm down, because that lets the readers know I like emotionally intense stuff, and this one rated highly on a emotional intensity scale!