AI Guides › Prompting
The Three-Part Prompt Structure Worth Memorising
By Nigel Guy · 2 min read
Most prompting frustration comes from missing one of three things, not from
a lack of cleverness in the wording. Once you notice the pattern, you can
check any weak prompt against it in seconds and usually find exactly which
part is missing.
The rule: role, task, and constraints — three parts, in that order, and a
prompt missing any one of them is missing something specific and fixable,
not just "unclear."
The three parts
- Role — who this is for, or what perspective it should take. Not
decoration ("you are a world-class expert") but genuine framing: "review
this as someone who's never seen the project before" changes the actual
output, not just the tone.
- Task — the specific thing to produce, stated as an action, not a
topic. "Write about the launch" is a topic. "Write a three-sentence
summary of the launch for someone who missed the meeting" is a task.
- Constraints — length, format, what to include, what to exclude, what
already exists that this shouldn't contradict. This is the part almost
everyone skips, and it's usually the part that determines whether the
first draft is usable or needs three more rounds.
The mechanism
When a response comes back wrong, check it against the three parts before
rewriting the whole prompt. Usually only one is missing or vague, and fixing
just that one is faster than starting over.
What to skip
Skip treating "role" as costume language — a role only helps if it
genuinely changes what's relevant to include, not if it's just flavour text.
Skip stacking constraints beyond what actually matters; three real
constraints beat ten where seven are noise.
Guardrails
- This structure improves the odds of a useful first draft. It doesn't
replace reviewing what comes back.
- Not every request needs all three parts stated explicitly — for a
familiar, repeated task, the role and task may already be understood from
context, and only the constraint needs stating.
- If you keep needing several rounds to get a usable answer to a similar
kind of request, that's a sign to save the working version as a template
rather than reconstructing it from scratch every time.
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