The honest answer is that 90% of cover letters get a 30-second skim or less. The reader is checking three things: does this candidate seem to actually know what the role is about, do they have one concrete moment that connects to it, and are they easy to talk to. That's it.
Everything else — the formatting, the salutation, the tone — is table stakes. Get them wrong and you get filtered out; get them right and they don't help you stand out. The three signal-bearing pieces are:
01
A specific opener that shows you understand the role.
Drawn from the JD itself, the company's product, or something concrete about the team. Not the generic mission statement.
02
One concrete moment from your resume that maps to a JD requirement.
Pick the strongest match. Spell out what you did, what came of it, and why that experience translates to what the role needs.
03
A confident, specific close.
Suggest the conversation, don't beg for it. "I'd welcome the chance to discuss how my work on X could fit your Y team" is doing more work than "I look forward to hearing from you."
Three paragraphs, ~250 words, three signal-bearing pieces. That's the architecture. Length, tone polish, and grammar are hygiene; the substance lives in those three places.