The headline grabs attention, so the description line should do the work of convincing. If your headline says what you offer, the description should explain why it matters or what the person gets from it. For example, if the headline is "Affordable Web Design Services," the description could explain the turnaround time, what is included, or why clients trust you. Repeating the same point in both wastes space. The description is your chance to give one more reason to click. What do you think is the most underused opportunity in a Google Ads description line?