If you can’t say the plan in one sentence, you don’t have a plan yet. You have a vibe.

Vagueness survives because it feels like agreement. While the plan stays fuzzy, nobody has to discover that they pictured different things, and the disagreement waits until the work is half done. Forcing it into one sentence is uncomfortable for exactly that reason: it makes the unresolved parts visible. That discomfort is the plan getting made.

Write yours in one sentence with a what, a who, and a when. If you cannot, the gap you keep bumping into is the decision you have not made yet. Make that one first and the sentence writes itself.