You rarely need all five building blocks every time, but knowing them gives you a checklist so nothing important is left to chance: Role, Task, Context, Format, Constraints.
A Concrete Example
Watch a weak prompt become strong by adding blocks one at a time:
Start: "Write an email about our launch." (task only — generic) Add role: "You are a marketing copywriter. Write an email about our launch." (better tone) Add context: "...about our new budgeting app launch for first-time savers." (now specific) Add format: "...as two short paragraphs with a CTA button." (now usable) Add constraints: "...under 150 words, warm but not pushy." (now polished)
Each block removes a guess. By the end, the AI has a real brief and the first draft is usable.
A complete prompt is just the five blocks stacked together.