Most cover letters written for Kenyan job applications fail for one of two reasons: they are either too stiff and formulaic ("I write to express my sincere interest in the above-referenced position") or so generic that they could have been sent to any employer for any role.
A good cover letter does one thing: it tells the recruiter something the CV it accompanies cannot. The CV lists what you did. The cover letter explains why you want this specific role at this specific organisation, and why you are the right person for it — in your own voice, in plain language.
For finance, banking, and economics roles in Kenya, the most effective cover letters are short — three paragraphs at most. The first paragraph names the role and makes one sharp claim about your fit. The second paragraph offers one or two specific, evidenced reasons why you are qualified — referencing something you built, a result you achieved, or a problem you solved. The third paragraph closes cleanly and requests a conversation, ideally setting you up for preparing for the interview that follows.
Do not repeat your CV in prose form. Do not use a template that starts "I am a highly motivated individual." Do not address it "To Whom It May Concern" if the recruiter's name is anywhere on the posting. These signals tell the reader that you did not try.
The best cover letters show that you read the job description carefully, understand what the employer is trying to solve, and can communicate precisely — much like tailoring your CV to the same role. That is itself a demonstration of the skills most knowledge-work employers are hiring for.