Writing a prompt can require you to recall facts, choose words, and organize an explanation at the same time. You may shorten it to avoid that effort. Some people find speaking easier; others think more clearly by writing. The question is which method helps you supply the information the task needs.
When speaking feels natural, describe the situation first and decide how to organize it afterward. The assistant can then summarize your goals, constraints, and open questions. That separates capturing the idea from editing the explanation, which can also be done with rough typed notes.
Exact wording sometimes deserves deliberate typing. A deadline, a quoted phrase, or a constraint may need careful revision before you submit it. Combining methods may fit: speak the background, attach the source, and type the wording that must remain exact.