Product Spec

Product Spec / PRD

Turn an idea into a spec you can build against and verify. A good spec is the input to verify-against-spec (coverage checking) and complete-feature (the build gate). Keep it tight — a PRD is a decision record, not an essay.

> Best spec length is "as short as possible while still removing ambiguity." If a sentence doesn't change what gets built or how it's tested, cut it.

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The template

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## Problem
Who has what problem, and the evidence it's real (support tickets, churn, a request count).
One paragraph. If you can't state the problem crisply, stop — you're not ready to build.

## Goals
- The outcomes this feature must achieve (user- or business-level, not implementation).

## Non-goals
- Explicitly out of scope. This list prevents scope creep and is half the value of the doc.

## User stories
- As a , I want  so that .
  (One per distinct need; each maps to acceptance criteria below.)

## Acceptance criteria
Given/When/Then, testable, unambiguous (see below). These ARE the definition of done.

## Success metrics
- The metric(s) that tell us it worked, with a target and a measurement window.
  (Tie to app-analytics; if you can't measure it, say how you'll judge success.)

## Scope / phases
- v1 (this spec) vs later. What's the smallest shippable slice?

## Risks & open questions
- Known unknowns, dependencies, and decisions still owed. Assign owners.

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Writing acceptance criteria that are actually testable

This is the part that determines whether the feature can be verified. Use Given / When / Then:

Given a signed-in user with an expired subscription
When they open the paywall
Then the "Restore Purchases" button is visible
And tapping it re-checks entitlements and unlocks if a valid purchase exists

Each criterion must be:

• Observable — a tester (or a test) can see pass/fail without reading your mind.
• Atomic — one behavior per criterion; split compound ones.
• Free of solution detail — say what, not how ("the list updates within 1s", not "call reload() on the diffable data source").
• Inclusive of edge/empty/error states — the empty list, the offline case, the rejected input. These are where features actually break.

Bad: "The feature should work well and be fast." Good: "When the search returns no results, an empty state with a 'Clear filters' action is shown."

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Goals vs non-goals — the scope contract

• A goal is an outcome: "Users can recover a deleted note within 30 days." Not "add a trash table."
• Non-goals are a feature, not an afterthought: "Not syncing trash across devices in v1" tells engineering what to not build and reviewers what not to flag as missing.
• If a stakeholder request isn't in Goals, it's a non-goal by default — make the important ones explicit.

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Success metrics

• Pick one primary metric (the thing that must move) plus a couple of guardrails (things that must not get worse, e.g. crash rate, retention).
• State a target and window: "lift activation from 40% → 50% within 4 weeks of launch."
• If the feature is hard to quantify, define a qualitative bar and how you'll judge it. "No measurement plan" is itself a risk to list.

See app-analytics for instrumenting these, and app-store-pricing / asc-aso when the metric is revenue/conversion.

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Handoff

1. Draft the spec with the template above.
2. Resolve open questions or assign owners — don't start building on unresolved decisions.
3. Hand acceptance criteria to implementation; later run verify-against-spec to confirm coverage and complete-feature to gate the merge.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: markdavidgan
• Source: markdavidgan/apple-dev-skills
• License: MIT

Install and usage instructions live in the source repository linked above.