Writing Specs & Designs

Scope

Covers

• Producing a Spec & Design Doc Pack that helps product, design, and engineering quickly reach shared clarity
• Converting “insights” into concrete artifacts: a low‑fidelity diagram, flows/states, prototype plan, and testable acceptance criteria
• Mobile-specific tap economy (when relevant): explicitly optimizing taps and interaction cost

When to use

• “Write a spec / feature spec / technical spec for this feature.”
• “Turn these notes into a design doc that engineering can build from.”
• “Create a shaping-style doc with a diagram of the moving pieces.”
• “We need a prototype plan to evaluate the feel of this interaction.”

When NOT to use

• You’re still validating what problem to solve (do discovery / problem definition first).
• You need a high-level strategy/vision document (do product vision / north star work first).
• You need a deep engineering architecture design (APIs, schemas, scaling, reliability) rather than product interaction clarity.
• You only need pixel-perfect UI mocks (this produces specs and structured guidance, not final visuals).
• You need a decision-level PRD with requirements and success metrics but not build-ready flows -> use writing-prds
• You need expert design critique on an existing prototype -> use running-design-reviews
• You need to validate designs with real users -> use usability-testing
• You need to establish design-engineering handoff processes or design system standards -> use design-engineering

Inputs

Minimum required

• Feature/change: 1–2 sentence description
• Target users + primary use case (happy path)
• Platform(s): web / iOS / Android / desktop (call out mobile explicitly)
• Goals + non-goals (v1 boundaries)
• Constraints: timeline, dependencies, policy/legal/privacy, technical constraints
• Success metrics (1–3) + guardrails (2–5)

Missing-info strategy

• Ask up to 5 questions from references/INTAKE.md, then proceed.
• If key info remains missing, state assumptions explicitly and provide 2–3 options (scope/flows/prototype approach).

Outputs (deliverables)

Produce a Spec & Design Doc Pack in Markdown (in-chat; or as files if the user requests):

1. Context snapshot (problem, why now, goals/non-goals, constraints, stakeholders)
2. Low‑fidelity diagram of the moving pieces (≤10) + key decisions
3. User flows + states (happy path + top edge cases) with clear entry/exit points
4. Prototype brief (what to prototype, fidelity, timebox, data realism, success criteria)
5. Requirements + acceptance criteria (testable; must/should/could)
6. Measurement plan (metrics → data/events → owner → cadence)
7. Risks / Open questions / Next steps (always included)

Templates: references/TEMPLATES.md

Workflow (8 steps)

1) Choose the smallest artifact set that unblocks the team

• Inputs: User request + constraints.
• Actions: Decide whether to deliver: (a) Spec & Design Doc only, or (b) Spec & Design Doc + Prototype Brief emphasis (feel-critical).
• Outputs: Artifact selection + rationale.
• Checks: Artifacts match the decision being made (alignment vs build execution vs interaction feel).

2) Intake + context snapshot

• Inputs: references/INTAKE.md.
• Actions: Ask up to 5 questions; confirm audience/DRI, platform(s), constraints, and success metrics/guardrails.
• Outputs: Context snapshot section.
• Checks: You can state the problem, user, and success measure in 1–2 sentences.

3) Lock scope boundaries (and define “tap budget” if mobile)

• Inputs: Context snapshot.
• Actions: Write goals, non-goals, out-of-scope, assumptions, dependencies. For mobile flows, define a “tap budget” (max taps to value) and where attention is most fragile.
• Outputs: Scope boundaries + (optional) tap budget.
• Checks: “What we are NOT doing” is explicit; mobile value path has a clear tap target.

4) Draft the low‑fidelity diagram (the “shaping” output)

• Inputs: Scope + constraints.
• Actions: Produce a diagram that shows the moving pieces (≤10), data/hand-offs, and where UX decisions matter. Avoid pixel-level UI; prefer clarity of structure.
• Outputs: Low‑fidelity diagram + annotated decisions.
• Checks: A partner can say “I know what to build” without a meeting.

5) Specify user flows + states (make edge cases concrete)

• Inputs: Diagram + use case(s).
• Actions: Document entry points, happy path, and top edge cases; include error/empty/loading states, permissions, and copy notes where ambiguity causes bugs.
• Outputs: Flow + state table(s).
• Checks: Another person can role-play the flow; each edge case has an intended outcome.

6) Write the prototype brief (only where “feel” matters)

• Inputs: Flows/states + unknowns.
• Actions: Identify the 1–3 riskiest interaction uncertainties; specify prototype type (low-fi, hi-fi, or in-code), timebox, realism (use real data where possible), and what “good” feels like.
• Outputs: Prototype brief.
• Checks: Prototype plan is testable (scenarios + success criteria), and explicitly disposable if using throwaway code.

7) Convert into testable requirements + acceptance criteria

• Inputs: Flows/states + prototype learnings (if any).
• Actions: Write requirements with acceptance criteria (must/should/could). Include non-functional needs (accessibility, performance, privacy) and instrumentation needs.
• Outputs: Requirements section.
• Checks: Engineering/QA can derive test cases without re-interpreting intent.

8) Quality gate + finalize for circulation

• Inputs: Full draft pack.
• Actions: Run references/CHECKLISTS.md and score with references/RUBRIC.md. Add Risks/Open questions/Next steps and clearly mark decisions vs assumptions.
• Outputs: Final Spec & Design Doc Pack (shareable as-is).
• Checks: Owners, metrics, and open questions are explicit; the diagram + flows remove the biggest ambiguities.

Quality gate (required)

• Use references/CHECKLISTS.md and references/RUBRIC.md.
• Always include: Risks, Open questions, Next steps.

Examples

Example 1 (mobile flow): “Write a spec + design doc for a new ‘invite friends’ flow in our iOS app. Goal: increase successful invites; minimize taps to first value.”
Expected: tap budget + flow/state tables, a low-fi diagram of screens/transitions, and a prototype brief for the critical interaction.

Example 2 (B2B web feature): “Create a design doc/spec for ‘bulk edit roles’ for admins. Include edge cases and acceptance criteria.”
Expected: permissions-focused flows/states, requirements with acceptance criteria, and a measurement plan.

Boundary example (redirect): “We need to decide whether to build this feature and align stakeholders on requirements and success metrics.” Response: redirect to writing-prds -- this request is about decision-level alignment and requirements, not build-ready interaction specs and flows.

Boundary example (insufficient context): “Write a spec to ‘improve engagement’ (no product context, no user, no success metric).” Response: ask the minimum intake questions; if still missing, provide 2-3 scoped options + assumptions and recommend upstream discovery before committing to a spec.

Anti-patterns

Avoid these common failure modes when writing specs and design docs:

1. Diagram-as-decoration -- Including a diagram that restates the text without showing moving pieces, data flow, or decision points. The diagram should reveal structure that prose cannot.
2. Happy-path-only flows -- Documenting only the ideal path and omitting error, empty, loading, and permission states. Edge cases discovered during build are 10x more expensive to handle.
3. Prototype without a question -- Proposing a prototype brief without a clear hypothesis or success criteria. Every prototype must answer a specific design uncertainty.
4. Spec-as-PRD -- Including strategic rationale, market context, or stakeholder alignment content that belongs in a PRD. Specs should assume the “what” and “why” are decided and focus on “how it works.”
5. Missing platform specifics -- Writing platform-agnostic flows when the feature has mobile-specific constraints (tap economy, notifications, offline states). Always call out platform differences explicitly.