reverse-document

name	reverse-document
description	Generate design or architecture documents from existing implementation. Works backwards from code/prototypes to create missing planning docs.
argument-hint	<type> <path> (e.g., 'design src/api/auth' or 'architecture src/core')
user-invocable	true
allowed-tools	Read, Glob, Grep, Write, Edit, Bash
effort	3

Reverse Documentation

This skill analyzes existing implementation (code, prototypes, systems) and generates appropriate design or architecture documentation. Use this when:

• You built a feature without writing a design doc first
• You inherited a codebase without documentation
• You prototyped a mechanic and need to formalize it
• You need to document "why" behind existing code

---

Workflow

1. Parse Arguments

Format: /reverse-document <type> <path>

Type options:

• design → Generate a product design document (PRD section)
• architecture → Generate an Architecture Decision Record (ADR)
• concept → Generate a concept document from prototype

Path: Directory or file to analyze

• src/api/auth/ → All combat-related code
• src/core/event-system.cpp → Specific file
• prototypes/stealth-mech/ → Prototype directory

Examples:

/reverse-document design src/api/payment
/reverse-document architecture src/core/entity-component
/reverse-document concept prototypes/vehicle-combat

2. Analyze Implementation

Read and understand the code/prototype:

For design docs (PRD):

• Identify mechanics, rules, formulas
• Extract business logic values (damage, cooldowns, ranges)
• Find state machines, ability systems, progression
• Detect edge cases handled in code
• Map dependencies (what systems interact?)

For architecture docs (ADR):

• Identify patterns (ECS, singleton, observer, etc.)
• Understand technical decisions (threading, serialization, etc.)
• Map dependencies and coupling
• Assess performance characteristics
• Find constraints and trade-offs

For concept docs (prototype analysis):

• Identify core mechanic
• Extract emergent business patterns
• Note what worked vs what didn't
• Find technical feasibility insights
• Document user fantasy / feel

3. Ask Clarifying Questions (Collaborative Protocol)

DO NOT just describe the code. ASK about intent:

Design questions:

• "I see a stamina system that depletes during combat. Was this for:
  • Pacing (prevent spam)?
  • Resource management (strategic depth)?
  • Or something else?"
• "The stagger mechanic seems central. Is this a core pillar, or supporting feature?"
• "Damage scales exponentially with level. Intentional power fantasy, or needs rebalancing?"

Architecture questions:

• "You're using a service locator pattern. Was this chosen for:
  • Testability (mock dependencies)?
  • Decoupling (reduce hard references)?
  • Or inherited from existing code?"
• "I see manual memory management instead of smart pointers. Performance requirement, or legacy?"

Concept questions:

• "The prototype emphasizes stealth over combat. Is that the intended pillar?"
• "Users seem to exploit the grappling hook for speed. Feature or bug?"

4. Present Findings

Before drafting, show what you discovered:

I've analyzed src/api/auth/. Here's what I found:

MECHANICS IMPLEMENTED:
- 3-hit combo system with timing windows
- Guard-break mechanic (heavy attack vs blocking enemy)
- Stamina system (depletes on attack/dodge, regens when idle)
- Stagger system (builds up, triggers vulnerable state)

FORMULAS DISCOVERED:
- Damage = Base * (1 + StrengthScaling * Level)
- Stagger buildup = AttackStaggerValue / (Enemy.Poise * 0.5)
- Stamina cost = BaseStaminaCost * (1 - EfficiencyBonus)

UNCLEAR INTENT AREAS:
1. Stamina system — pacing or resource management?
2. Stagger — core pillar or supporting feature?
3. Damage scaling — power fantasy or needs tuning?

Before I draft the design doc, could you clarify these points?

Wait for user to clarify intent before drafting.

5. Draft Document Using Template

Based on type, use appropriate template:

Type	Template	Output Path
design	templates/design-doc-from-implementation.md	design/docs/[system-name].md
architecture	templates/architecture-doc-from-code.md	docs/architecture/[decision-name].md
concept	templates/concept-doc-from-prototype.md	prototypes/[name]/CONCEPT.md or design/concepts/[name].md

Draft structure:

• Capture what exists (mechanics, patterns, implementation)
• Document why it exists (intent clarified with user)
• Identify what's missing (edge cases not handled, gaps in design)
• Flag follow-up work (balance tuning, missing features)

6. Show Draft and Request Approval

Collaborative protocol:

I've drafted the combat system design doc based on your code and clarifications.

[Show key sections: Overview, Mechanics, Formulas, Design Intent]

ADDITIONS I MADE:
- Documented stamina as "pacing mechanic" per your clarification
- Added edge cases not in code (what if stamina hits 0 mid-combo?)
- Flagged balance concern: exponential damage scaling at high levels

SECTIONS MARKED AS INCOMPLETE:
- "Enemy AI interaction with stagger" (not fully implemented yet)
- "Weapon variety and scaling" (only sword implemented so far)

May I write this to design/docs/combat-system.md?

Wait for approval. User may request changes before writing.

7. Write Document with Metadata

When approved, write the file with special markers:

---
status: reverse-documented
date: 2026-02-13
verified-by: [User name]
---

# Combat System Design

> **Note**: This document was reverse-engineered from the existing implementation.
> It captures current behavior and clarified design intent. Some sections may be
> incomplete where implementation is partial or intent was unclear.

[Rest of document...]

8. Flag Follow-Up Work

After writing, suggest next steps:

✅ Written to design/docs/combat-system.md

FOLLOW-UP RECOMMENDED:
1. Run /balance-check on combat formulas (exponential scaling concern)
2. Create ADR for stamina system architecture decision
3. Implement missing edge cases:
   - Stamina depletion mid-combo behavior
   - Stagger state during dodge
4. Extend design doc when weapon variety is implemented

Would you like me to tackle any of these now?

---

Template Selection Logic

If analyzing...	Use template...	Because...
src/api/*	design-doc-from-implementation.md	Business mechanics → PRD
src/core/*, src/ai/*	architecture-doc-from-code.md	Core systems → ADR
prototypes/*	concept-doc-from-prototype.md	Experiments → concept doc
src/networking/*	architecture-doc-from-code.md	Technical systems → ADR
src/ui/*	design-doc-from-implementation.md	UI/UX → design spec

---

Example Session: Reverse-Document Combat Code

User: /reverse-document design src/api/auth

Agent: I'll analyze your combat implementation to create a design doc.
       [Reads code, discovers mechanics, formulas]

Agent: I've analyzed src/api/auth/. Here's what I found:
       [Shows mechanics, formulas, unclear areas]

       Before drafting, could you clarify:
       1. Stamina system intent?
       2. Is stagger a core pillar?
       3. Damage scaling — intentional or needs tuning?

User: 1. Stamina is for pacing, prevent button mashing
      2. Stagger is core — I want deliberate combat
      3. Yeah, exponential is too much, should be linear

Agent: Perfect, that clarifies the vision. Let me draft the design doc.
       [Shows draft with clarified intent]

       May I write this to design/docs/combat-system.md?

User: Yes, write it.

Agent: ✅ Written to design/docs/combat-system.md
       ✅ Marked as [REVERSE-DOCUMENTED]
       ✅ Flagged damage scaling for rebalancing

       Next steps:
       - Update damage formula to linear scaling
       - Run /balance-check to validate progression curve
       - Document stagger as core pillar in product-pillars.md

---

Collaborative Protocol

This skill follows the collaborative design principle:

1. Analyze First: Read code, understand implementation
2. Question Intent: Ask about "why", not just "what"
3. Present Findings: Show discoveries, highlight unclear areas
4. User Clarifies: Separate intent from accidents
5. Draft Document: Create doc based on reality + intent
6. Show Draft: Display key sections, explain additions
7. Get Approval: "May I write to [filepath]?"
8. Flag Follow-Up: Suggest related work, don't auto-execute

Never assume intent. Always ask before documenting "why".

Protocol

• Question: Analyzes code, then asks about design intent — never assumes "why" from "what"
• Options: Type drives template — design → PRD, architecture → ADR, concept → concept doc
• Decision: User clarifies intent for all unclear areas before the draft is written
• Draft: Draft shown with additions and uncertainty flags before saving
• Approval: "May I write to design/docs/[system].md?" (or architecture/concept path)

Output

Deliver exactly:

• Document type — design, architecture, or concept (based on argument)
• Generated document saved to design/specs/[name].md or docs/technical/[name].md
• Uncertainty flags — sections where intent was inferred rather than confirmed (user must verify)
• Follow-up suggestions — related docs that are also missing