Writing Feature Specs
Part of the Product Management Roadmap
In short
A feature spec zooms into one feature in detail: states, rules, errors. A good one answers engineers' questions before they ask them.
A lighter-weight sibling of a PRD, focused narrowly on describing exactly how one feature should behave — often the artifact engineers reference daily during implementation.
Think of it like this
A proper recipe card
"Add some masala and cook till done" works for Nani, not for a new cook. A real recipe says how much, how long, what it should look like, and what to do if it sticks. Specs give engineers that clarity.
Watch it happen
A spec answering questions in advance
What if list is empty?
1/6Building a saved-jobs list, the engineer hits the empty case and checks the spec.
The big ideas
What you need to know
List every state
Loading, empty, filled, error, offline, no permission. Each needs a decision.
Write the rules
Limits, sorting, who can see what, what happens on delete. Rules are where bugs hide.
Spell out errors
For each failure, say what the user sees and what they can do next.
Link, don't repeat
Link to designs and the PRD instead of copying them. One source of truth each.
Save yourself the pain
Common mistakes
Oops
Specifying only the filled, happy state.
Do this instead
List all states and errors. Empty and error states are where users get stuck.
Oops
Writing a spec nobody reviews before the sprint.
Do this instead
Walk through it with engineering and design before work starts, and fix gaps together.
Your mission
Spec a small feature
Quick check
Which section most often prevents surprise bugs in a feature spec?
Go deeper
- 1Write a feature spec for one user story from your practice PRD.
- 2Include specific input/output behavior, not just a general description.
- 3Get feedback from someone technical on whether it's implementable as written.
More topics at this stop
Writing a PRD (Product Requirements Doc)
User Stories & Acceptance Criteria
Epics vs Stories vs Tasks
One-Pagers & RFCs
Edge Case Thinking
Non-Functional Requirements
Wireframing Basics
Writing for Engineers vs Executives
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