pedantic
Overly focused on tiny details in an annoying way.
Pedantic means being overly concerned with minor details and rules, especially in a way that shows off knowledge or becomes annoying. A pedantic person might interrupt a good story to correct tiny facts that don't really matter, like pointing out that the movie you're describing came out in 2019, not 2020, when everyone understands what you meant.
There's a difference between being careful and being pedantic. A careful editor catches real mistakes that confuse readers. A pedantic editor wastes time arguing about comma placement that nobody will notice. When your friend explains the rules of a card game clearly, that's helpful. When they stop the game every minute to lecture about obscure rules nobody cares about, that's pedantic.
Today, calling someone pedantic suggests they care more about looking smart than about actually communicating well. Scientists need precision in their experiments, but a pedantic scientist might bore everyone at dinner by correcting the technical accuracy of casual conversation. Precision matters in the right context; being pedantic means losing sight of what actually matters in the moment.