document-feature

name	document-feature
description	Interview a developer to produce a living feature doc at docs/feature/{slug}.md, capturing user value, architecture (with ADR links), and data/user flow with at least one Mermaid diagram. Use when the user says "document this feature", "write a feature doc", "create docs/feature/X", "explain feature X for new devs", or asks to onboard future engineers onto a shipped feature. Different from /create_plan (forward-looking design) and Epics (scope/sprint planning) — this is the present-tense "what does this thing do today" doc for engineers reading the codebase cold.
disable-model-invocation	true
model	sonnet
effort	high

document-feature

What this is, what this isn't

docs/feature/{slug}.md is the living, present-tense doc for a shipped feature. Adjacent doc types serve different purposes:

• thoughts/designs/ — forward-looking proposals (past-tense once shipped)
• thoughts/epics/ — scope and milestone planning
• thoughts/plans/ — the build roadmap for an epic
• docs/adr/ — point-in-time decisions

A feature doc tells a future engineer (human or LLM agent) what the feature does today and where to look. It is not a design history.

Quick start

User: /document-feature lead-conversation-history
→ Recon → Interview (3 pillars) → Draft → Plain-language pass → Update index

Output: docs/feature/lead-conversation-history.md + an entry in docs/feature/README.md.

Workflow

1. Recon (read code first, ask less)

• Resolve {slug} from user input.
• Check docs/feature/{slug}.md — if it exists, ask: update or replace?
• Grep code for the feature; identify file paths and route segments.
• List ADRs in docs/adr/ that may relate.
• Find GitHub issues/PRs: gh issue list --search "{slug}", gh pr list --search "{slug}", and git log --oneline --grep="{slug}" to surface PRs that shipped the feature. Capture issue numbers for the frontmatter related-issues: field.
• Fast-path: if thoughts/designs/*-{slug}.md exists, read it first and pre-fill draft answers — the interview then verifies and updates rather than gathering from scratch.
• Surface findings to the user before starting the interview.

2. Interview (3 pillars, one Q at a time)

Methodology: one question at a time, propose a recommended answer when the codebase suggests one, explore code instead of asking when answerable. Full bank in INTERVIEW.md.

• P1 — User value: who is the user, what problem does this solve, what's out of scope, how do we know it works?
• P2 — Design + ADRs + ops: where does this live in code, what was the design choice (and what was rejected), which ADRs apply, what logs/alerts/flags signal health, what are the failure modes?
• P3 — Flow: what triggers it (UI, cron, webhook — list all), what data path does it follow, what state changes happen, what are the edges?

3. Draft

• Load TEMPLATE.md; write to docs/feature/{slug}.md.
• Embed at least one Mermaid diagram in the Flow section. Pick by content:
  • sequenceDiagram — ≥2 actors with ordered messages
  • flowchart LR — single-actor branching logic
  • stateDiagram-v2 — explicit state transitions
  • graph TD / graph LR — feature spans ≥3 services/modules
• Mirror the diagram styles already proven in docs/README.md so they render in the existing stack.
• Cross-link ADRs/designs/epics via relative paths (see docs/adr/adr001-imessage-integration-for-sales-automation.md Links section).

4. Plain-language pass

• Apply rules from PLAIN-LANGUAGE.md — two zones: explain-mode (~grade 6) for user-value sections, tech-mode (~grade 9-10) for architecture/flow.
• Invoke the writing-clearly-and-concisely skill on the draft for the final pass.

5. Update index

• Append/update docs/feature/README.md: one line per slug, sorted alphabetically. Format: - [Feature Name](slug.md) — one-line description from doc's intro.
• Bootstrap on first run with a brief explainer paragraph framing what docs/feature/ is.

Behavioural rules

• Do not create ADRs. If a hard-to-reverse decision surfaces without one, flag inline with > [!NOTE] Missing ADR: <decision>. Recommend /domain-model. Defer creation to the domain-model skill.
• Frontmatter required fields: status: living, last-updated: YYYY-MM-DD, related-adrs:, related-design:, related-epic:, related-issues: (GitHub issue/PR numbers — gh issue list and git log for the slug surface candidates).
• Bootstrap docs/feature/ if it does not exist; the first feature doc creates the directory.

See also

• INTERVIEW.md — full question bank with skip-if conditions.
• PLAIN-LANGUAGE.md — Strunk rules, compression principles, replaceable-pattern checklist.
• TEMPLATE.md — output skeleton with frontmatter and Mermaid placeholders.