The whole book · one sentence
"Ask questions about their life so good that even your mom couldn't lie to you."
— Rob Fitzpatrick · The Mom Test
The 3 rules · tape to laptop
Run every question through these three.
01
Rule 01
Their life, not your idea.
02
Rule 02
Past specifics, not future generics.
03
Rule 03
Listen. Talk <20%.
The 3 killer questions · steal verbatim
What to ask.
Killer · 01
"Walk me through the last time you tried to [do X]."
Past tense + specific story. Listen for friction, not features.
Killer · 02
"What have you tried? What did it cost?"
Real pain + real wallet. $0 spent = walk away.
Killer · 03
"Who else has this? Would you intro me?"
Intros = real validation. Free truth-test.
The 3 deadly questions · never ask
What not to ask.
Deadly · 01
"Do you think this is a good idea?"
Triggers politeness. Asks for opinion, not behavior.
Deadly · 02
"Would you use a product that...?"
Hypothetical future. "Yes" predicts nothing about their wallet.
Deadly · 03
"How much would you pay for this?"
Polite over-commitment. Real price = 1/3 of stated.
Replace "would" with "did". Replace "if" with "when".
After every interview · spot the signal
Real signal vs polite signal.
Real signal · keep going
- Specific story with dates, names, $
- Already spent money trying to solve it
- Has a workaround (spreadsheet, intern, hack)
- Introduced you to others with the same problem
- Asked when they could try it
- Got visibly frustrated describing it
Polite signal · be honest
- Said "that sounds cool" a lot
- Gave feature ideas not problem stories
- Never spent money on this
- Said "I'd use it" but couldn't name when
- Told you what "people like them" need
- Stayed abstract the whole time
Score each side 1–5 after every interview.
If polite > real across 3 interviews, pivot to your #2 idea Monday. No ego.
→ Use the
interactive scorecard
Pocket prompt · world-class format
Generate your script with Claude.
Paste into Claude · fill the brackets (or use Prompt 00 to auto-fill)
# ROLE
You are a Y Combinator partner with 15 years of experience watching founders interview users badly. You've coached 500+ early-stage founders. Your superpower is sniffing out questions that trigger politeness instead of behavior.
# GOAL
Write a Mom-Test-grade interview script I can use TODAY — sharp, tuned to my exact idea and user, not a generic template.
# CONTEXT (fill in, or ask me)
- My one-line idea: [ONE-LINE IDEA]
- My target user: [PROFILE — role, where they hang out]
- My riskiest assumption: [WHAT I'M HOPING IS TRUE]
- Interviews done so far: [NONE / 1 / 2 / SUMMARIZE]
# CONSTRAINTS
- 5 questions, broad → specific
- Every question about PAST behavior, never hypotheticals
- Never mentions my product or uses "would" / "if"
- 2 follow-up probes per question, ~25 min total
# OUTPUT
1. Intro line I read aloud
2. 5 numbered questions with probes + what real signal sounds like
3. Closing: ask for 2 intros
# SELF-CHECK
Run each question through: past tense? specific? no "would"? no pitch? Rewrite any that fail. Tell me which was hardest and why.
💡 Pro tip: If you've already chatted with Claude about your project, paste Prompt 00 (auto-context) first — Claude will fill the brackets for you using prior context. See the full prompt pack.