Handbook
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Product & Engineering
How to Write a Product Spec
A good product spec aligns the team and prevents wasted work. Here's a simple format that works for startups.
Product specs have a bad reputation. In big companies, they’re often bureaucratic documents that delay shipping. In startups, they’re often skipped entirely, leading to confusion and rework.
The right answer is a lightweight spec that clarifies thinking and aligns the team without slowing you down.
Why Specs Matter
Alignment
Specs ensure everyone understands what’s being built and why. Without them, engineers interpret requirements differently, designers solve different problems, and stakeholders expect different outcomes.
Clear Thinking
Writing forces clarity. If you can’t explain what you’re building in a document, you don’t understand it well enough to build it.
Reduced Rework
Catching misunderstandings before code is written is 10x cheaper than catching them after. Specs surface questions and disagreements early.
Documentation
Specs become institutional memory. Why did we build this? What were the constraints? What did we consider and reject?
The One-Page Format
For most features at a startup, you need a one-page spec. No more.
Header
Feature: [Name]
Author: [Your name]
Date: [When written]
Status: [Draft / In Review / Approved]
Problem Statement (2-3 sentences)
What problem are we solving? For whom? Why does it matter?
Example:
Users currently can’t export their data, which prevents them from using our data in other tools. We’ve received 50+ support requests for this feature, and 3 churned customers cited it as their reason for leaving.
Goal (1-2 sentences)
What does success look like? How will we measure it?
Example:
Users can export their data to CSV or JSON. Success is 20% of active users exporting within the first month.
Non-Goals (bullet points)
What are we explicitly not doing? This prevents scope creep.
Example:
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Not building scheduled/automated exports (future consideration)
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Not supporting Excel format initially
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Not building import functionality in this release
Proposed Solution (paragraphs + visuals)
How will we solve the problem? Include:
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User flow
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Key screens (wireframes or mockups)
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Edge cases
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Technical approach (if relevant)
Keep it to the minimum needed for clarity. For small features, a few sentences. For complex features, more detail.
Open Questions
What haven’t you figured out yet? List questions that need answers before or during implementation.
Example:
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Should exports include archived items?
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What file size limits should we enforce?
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How do we handle exports that take longer than 30 seconds?
Alternatives Considered
What other approaches did you think about? Why did you reject them?
Example:
We considered building an API for programmatic exports but decided to start with UI-based exports because most users requesting this feature are non-technical.
When to Spec
Not everything needs a spec. Use this guide:
Write a spec for:
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New features that multiple people will work on
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Changes to core functionality
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Features with ambiguous requirements
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Anything that crosses team boundaries
Skip the spec for:
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Bug fixes
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Minor improvements with obvious scope
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Experiments you’ll throw away
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Work only one person is doing who doesn’t need alignment
When in doubt, write a lightweight spec. It takes 30 minutes and can save hours of rework.
Spec Writing Tips
Start with the Problem
Don’t jump to solutions. Clearly articulate the problem first. If the problem isn’t clear, the solution probably isn’t right.
Be Specific
“Make it easier” is not a spec. “Reduce clicks from 5 to 2” is. Specificity enables evaluation.
Use Real Examples
Instead of abstract descriptions, walk through a concrete example. “User Jane wants to export her Q4 sales data to analyze in Google Sheets.”
Include Visuals
A wireframe, flowchart, or mockup is worth a thousand words. Even rough sketches clarify intentions.
Name Your Assumptions
Make assumptions explicit. “We’re assuming users have modern browsers.” “We’re assuming less than 10% of users will use this feature.”
Keep It Updated
A spec that doesn’t match what was built is misleading. Update specs when plans change significantly.
Reviewing Specs
Who Reviews
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Engineering lead (technical feasibility)
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Designer (UX implications)
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Stakeholder (business value)
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Anyone who will be affected
What to Look For
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Is the problem clearly stated?
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Does the solution address the problem?
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Are there edge cases not covered?
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Is scope clearly bounded?
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Are the open questions answerable?
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Is this the right thing to build now?
Feedback Style
Focus on understanding, not criticism:
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“What happens when X?”
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“How does this interact with Y?”
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“Have you considered Z?”
Avoid rewriting their spec. Ask questions that help them improve it.
After the Spec
Kick-off
Before implementation, review the spec with the team. Walk through it together. Surface questions. Align on scope.
Reference During Build
Use the spec as the source of truth. When questions arise, check the spec. When scope creeps, point to the spec.
Update as You Learn
Implementation reveals things the spec didn’t anticipate. Update the spec to reflect reality. The goal is documentation, not perfection.
Retrospect
After launch, briefly note: Did we build what we spec’d? Did it solve the problem? What would we do differently?
Anti-Patterns
The Novel
A 30-page document for a simple feature. Overkill wastes time and often indicates unclear thinking.
The Handwave
“We’ll figure it out during implementation.” Maybe, but you’ll figure out the wrong things. Write down your plan.
The Solution in Search of a Problem
Jumping to solution without articulating the problem. Always start with why.
The One-Way Document
Written, never discussed, rarely referenced. Specs are for alignment, not checkbox compliance.
The Spec that Never Ships
Endless revisions, endless reviews, never good enough to build. Set a deadline and ship it.
Key Takeaways
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Specs align teams and clarify thinking without bureaucracy
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Use a one-page format: problem, goal, non-goals, solution, open questions, alternatives
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Write specs for features with ambiguous requirements or multiple people involved
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Start with the problem, be specific, include visuals
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Review specs collaboratively, update them as you learn
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The goal is alignment and documentation, not perfection
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