LESSON 5 OF 5
Turn what works into a system
BY THE END OF THIS LESSON
Convert a one-off good prompt into something reusable and testable.
The problem with brilliant one-offs
You write a prompt that produces something genuinely good. Two weeks later you need it again, half-remember it, and get something worse. The value was never in the individual answer — it was in the prompt, and you did not keep it.
Anatomy of a reusable prompt
Fixed part — role, constraints, format, exclusions. Never changes.
Variable part — clearly marked placeholders like [AUDIENCE] and [SOURCE MATERIAL].
Examples — one or two, kept with the prompt so they never get lost.
If you cannot tell at a glance which parts to edit, you will edit the wrong ones under time pressure.
Test it like a small piece of software
Run a new template on three inputs before trusting it: a typical case, an awkward case, and a case that should fail. The third matters most — if a template confidently handles input it should have refused, it will do that quietly in real use.
When a template starts underperforming, change one thing at a time. Rewriting the whole prompt tells you nothing about what was wrong.
WORKED EXAMPLE
ONE-OFF
Summarise this call transcript for me, focusing on the decisions and who owns what, in bullets.
TEMPLATE
ROLE: You summarise internal meetings for people who did not attend. INPUT: [TRANSCRIPT] OUTPUT, in this order: 1. Decisions made — one line each. If none, write "No decisions made". 2. Owners and deadlines — name, task, date. Write "no date given" rather than inferring one. 3. Open questions — anything raised and not resolved. 4. Disagreements — who disagreed on what, even if it was resolved. Rules: no preamble. Do not summarise discussion that led nowhere. Never invent a deadline. EXAMPLE: [one worked example kept attached]
Section 4 is the kind of thing you only think of once. Kept in a template it applies every time; retyped from memory it is the first thing to get dropped.
YOUR TURN
Stress-test a template before you rely on it.
RUN THIS
Here is a prompt template I want to reuse. Before I trust it, break it. Give me three test inputs: one typical, one awkward or messy, and one where the correct behaviour is to refuse or flag a problem rather than produce output. Run the template on all three, show the results, then tell me which instruction is missing based on how it behaved. Template: [paste yours]
What a good result looks like
The third test is the one that matters. If it produces a confident answer where it should have flagged a problem, you have found the missing rule.
KNOWLEDGE CHECK
Answer all 3 correctly to complete this lesson.
1. Which test case teaches you the most about a new template?
2. A template that used to work has degraded. What should you do?
3. Why mark placeholders clearly in a template?
REMEMBER THIS
Save the prompt, mark what varies, and test it on a case that should fail.