A marketing analyst wants a foundation model to generate product descriptions that follow the company's very specific style: a punchy one-line headline, exactly three bullet points, and a closing call-to-action. When they simply describe these rules in a plain instruction, the model's output is inconsistent — sometimes it skips the call-to-action or writes four bullets. The analyst does not have a labeled dataset and needs a quick fix without any training. Which prompt engineering technique should they apply first?