Keep it short. Unless your synopsis and summary are actively off-putting, they should generally serve as a flag to indicate to the reader where they are beginning and then as a guide to the story beyond the extract submission.
Missing out excessive detail is exactly the point. Related themes may play out in all your stories, like the leitmotif of a musical phrase but each story is inherently different from the other, right? Here, it will begin to look like a story, but an incredibly sparse and drab one.
A potential reader might ask for a summary, a journalist might want enough of an idea to start planning their piece, an advertiser or marketer might need the gist to plan a great campaign, or a blurb writer might need the key details to ply their craft well.
What about if you only had two sentences? A synopsis conveys the narrative arc, an explanation of the problem or plot, the characters, and how the book or novel ends.
Agents look for good writing skills. Again, your synopsis needs to be designed around core information — there is room for color, just not where it distracts, complicates, or bores.
The book synopsis is that three- or four-page snapshot of the book, that essentially tells your story from beginning to end, while seemingly stripping it of any intrigue, humor, or emotional resonance. Read through, with a focus on character arc.