# Spec

> Use when defining or changing WHAT to build - a new feature idea, a PRD to write or update, or scope that needs challenging before implementation starts.

- Skill: `omexit/spec` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add omexit/spec`
- Raw SKILL.md: https://api.skillmd.com/api/skills/omexit/spec/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Product & Planning
- Author: OmexIT (https://skillmd.com/u/omexit)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/omexit/spec

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# Product spec (PRD-first)

An approved PRD records intended behavior. Live implementation, decisions, and external source-of-truth contracts can reveal that it is stale. Classify divergence before editing: code defect, undocumented approved change, stale spec, or unresolved decision. Reconcile the authoritative artifact instead of copying drift silently.

## Mode detection
- **Challenge** - user is unsure whether to build: run only the scope gate, report, stop.
- **Create** - no PRD covers this area.
- **Update** (most common) - a PRD exists: surgical edits only.

## Scope gate (always, before writing anything)
Answer in five lines; recommend kill or shrink when answers are weak:
1. What user problem does this solve - who, doing what, blocked how?
2. What is the smallest version that solves it? Everything else goes to "later".
3. Can existing functionality already do this?
4. Cost vs measurable business value: implementation + operational + maintenance, against what it directly contributes to the core product.
5. Why now?

## Create mode
- Clarify only what's genuinely missing - one question at a time, multiple-choice where possible (persona, problem, success measure, constraints).
- Find the repo's PRD home (`docs/prd/`, `docs/prd.md`, `PRODUCT.md`) and match its structure; otherwise use `assets/prd-template.md`.
- Every non-trivial P0 requirement: Given/When/Then acceptance criteria plus at least two materially different edge cases. Do not invent filler for a genuinely atomic rule. NFRs are feature-specific; non-goals are mandatory.
- State system-of-record and ownership boundaries explicitly ("Service A is the system of record for loans; this service must not evolve into a loan-management system").
- Include a negative-constraints section: what must NOT be built or changed.

## Update mode
- Read the PRD and the source of truth (design doc, implementation, decision) first; produce a change map before editing.
- Preserve requirement IDs - update content, not IDs. Mark superseded requirements; never delete silently. Insert with sub-IDs (FR-017a). Add a version + change-log entry. Update cross-references.
- After editing, validate against the codebase: implemented-but-undocumented features, descoped requirements, contract drift.

## Self-review - spec smells
Flag before presenting: solution masquerading as requirement · vague metric ("improve UX") · missing non-goals · requirement without testable criteria · TBD without owner · "while we're at it" scope creep.

Run the Definition-of-Ready checklist from the template. Present for approval when approval is part of the repository workflow; implementation proceeds via `plan` once scope is explicit and authorized.