Add something new. Think of the title and the description as a single two-line pitch in the search result: the title says what the page is, and the description’s one job is to supply the reason to click that the title had no room for. The searcher reads exactly two lines from you, so if the second one only restates the first, you have spent your single follow-up saying nothing the title didn’t already say.
That is the cost of echoing the title, a wasted line in the one place a searcher is deciding between you and nine other results. The description should expand the title’s promise instead of repeating it: name the specific benefit, the proof, the detail, or the call to action the title left out. If the title is “How to Write Meta Descriptions,” the description should not be “Learn how to write meta descriptions”; it should add what the reader gets, a length guide, examples, a step-by-step workflow. Same topic, but the second line now carries information the first one didn’t.
This is not an argument against keyword overlap, and that distinction matters. The primary keyword can sit in both the title and the description, and Google bolds it in the snippet when it matches the query, which helps you stand out. Putting the keyword in both places is not the same as repeating the title. Place the keyword where it fits naturally, and still make the sentence around it deliver something new. The mistake is treating shared keywords as license to make the description a paraphrase of the title.
Read each description next to its own title and check what the second line adds. Where the description merely rewords the title, rewrite it so it does its own job, by giving the searcher a fresh, concrete reason to choose your result that the title alone did not provide.