www.ycombinator.com/blog/startup-school-week-1-recap-kevin-hale-and-eric-migicovsky/

Define the initial narrow customer segment. Explain who experiences the problem, what triggers it, how often it occurs, the cost of the current workaround and why solving it matters. Include both end users and economic buyers when different. Prefer evidence of customer behavior over survey enthusiasm.

Interview customers about the past: "Tell me about the last time this happened"; "What did you do?"; "Why was it hard?"; "What have you tried?"; "What did the workaround cost?" Do not lead the witness by pitching first. Record concrete patterns, objections, customers who do not care, and evidence contradicting the thesis. One useful structure is: WHO encounters PROBLEM when TRIGGER occurs, resorts to WORKAROUND and loses TIME/MONEY/OPPORTUNITY. Support with one or two real, sourced observations. Never fabricate quotes or interviews.

JUST-IN-TIME INPUT: Ask for specific customers, last-observed problem incidents, current substitutes, interviews, or direct usage evidence only as needed for this step. Capture missing evidence as an unknown instead of blocking the workflow.

Separate: Why did we choose this idea? What makes us unusually equipped to solve it? What do we know that others miss? Use personal experience, domain expertise, customer observation, distribution access or a technical breakthrough. Reject vague claims of passion or fascination with a hot sector.

A useful structure: "Most people assume X. We observed Y, supported by Z. That changes our approach: we do A rather than B." Only use this when truthful; not every startup needs an artificially contrarian insight. Show how insight affects product design, buying process or go-to-market. For "Why now?", identify a causal shift such as technical cost/performance, regulation, distribution, buyer behavior or economics. "AI is growing fast" alone is not sufficient.

FICTIONAL EXAMPLE: "The bottleneck isn't extracting invoice fields; it is reconciling inconsistent purchase orders, so we focus on matching before reporting." Verify before asserting it for a real company.

JUST-IN-TIME INPUT: Here, ask about the founders' relevant experiences, surprising observations and product decisions. Don't require a full founder biography at intake.