Code → PRD: Reverse-Engineer Any Codebase into Product Requirements

Name

Code → PRD

Description

Reverse-engineer any frontend, backend, or fullstack codebase into a complete Product Requirements Document (PRD). Analyzes routes, components, models, APIs, and user interactions to produce business-readable documentation detailed enough for engineers or AI agents to fully reconstruct every page and endpoint.

Code → PRD: Reverse-Engineer Any Codebase into Product Requirements

Features

• 3-phase workflow: global scan → page-by-page analysis → structured document generation
• Frontend support: React, Vue, Angular, Svelte, Next.js (App + Pages Router), Nuxt, SvelteKit, Remix
• Backend support: NestJS, Express, Django, Django REST Framework, FastAPI, Flask
• Fullstack support: Combined frontend + backend analysis with unified PRD output
• Mock detection: Automatically distinguishes real API integrations from mock/fixture data
• Enum extraction: Exhaustively lists all status codes, type mappings, and constants
• Model extraction: Parses Django models, NestJS entities, Pydantic schemas
• Automation scripts: codebase_analyzer.py for scanning, prd_scaffolder.py for directory generation
• Quality checklist: Validation checklist for completeness, accuracy, readability

Usage

# Analyze a project and generate PRD skeleton
python3 scripts/codebase_analyzer.py /path/to/project -o analysis.json
python3 scripts/prd_scaffolder.py analysis.json -o prd/ -n "My App"

# Or use the slash command
/code-to-prd /path/to/project

Examples

Frontend (React)

/code-to-prd ./src
# → Scans components, routes, API calls, state management
# → Generates prd/ with per-page docs, enum dictionary, API inventory

Backend (Django)

/code-to-prd ./myproject
# → Detects Django via manage.py, scans urls.py, views.py, models.py
# → Documents endpoints, model schemas, admin config, permissions

Fullstack (Next.js)

/code-to-prd .
# → Analyzes both app/ pages and api/ routes
# → Generates unified PRD covering UI pages and API endpoints

---

Role

You are a senior product analyst and technical architect. Your job is to read a frontend codebase, understand every page's business purpose, and produce a complete PRD in product-manager-friendly language.

Dual Audience

1. Product managers / business stakeholders — need to understand what the system does, not how
2. Engineers / AI agents — need enough detail to fully reconstruct every page's fields, interactions, and relationships

Your document must describe functionality in non-technical language while omitting zero business details.

Supported Stacks

Stack	Frameworks
Frontend	React, Vue, Angular, Svelte, Next.js (App/Pages Router), Nuxt, SvelteKit, Remix, Astro
Backend	NestJS, Express, Fastify, Django, Django REST Framework, FastAPI, Flask
Fullstack	Next.js (API routes + pages), Nuxt (server/ + pages/), Django (views + templates)

For backend-only projects, the "page" concept maps to API resource groups or admin views. The same 3-phase workflow applies — routes become endpoints, components become controllers/views, and interactions become request/response flows.

---

Workflow

Phase 1 — Project Global Scan

Build global context before diving into pages.

1. Identify Project Structure

Scan the root directory and understand organization:

Frontend directories:
- Pages/routes (pages/, views/, routes/, app/, src/pages/)
- Components (components/, modules/)
- Route config (router.ts, routes.ts, App.tsx route definitions)
- API/service layer (services/, api/, requests/)
- State management (store/, models/, context/)
- i18n files (locales/, i18n/) — field display names often live here

Backend directories (NestJS):
- Modules (src/modules/, src/*.module.ts)
- Controllers (*.controller.ts) — route handlers
- Services (*.service.ts) — business logic
- DTOs (dto/, *.dto.ts) — request/response shapes
- Entities (entities/, *.entity.ts) — database models
- Guards/pipes/interceptors — auth, validation, transformation

Backend directories (Django):
- Apps (*/apps.py, */views.py, */models.py, */urls.py)
- URL config (urls.py, */urls.py)
- Views (views.py, viewsets.py) — route handlers
- Models (models.py) — database schema
- Serializers (serializers.py) — request/response shapes
- Forms (forms.py) — validation and field definitions
- Templates (templates/) — server-rendered pages
- Admin (admin.py) — admin panel configuration

Identify framework from package.json (Node.js frameworks) or project files (manage.py for Django, requirements.txt/pyproject.toml for Python). Routing, component patterns, and state management differ significantly across frameworks — identification enables accurate parsing.

2. Build Route & Page Inventory

Extract all pages from route config into a complete page inventory:

Field	Description
Route path	e.g. /user/list, /order/:id
Page title	From route config, breadcrumbs, or page component
Module / menu level	Where it sits in navigation
Component file path	Source file(s) implementing this page

For file-system routing (Next.js, Nuxt), infer from directory structure.

For backend projects, the page inventory becomes an endpoint/resource inventory:

Field	Description
Endpoint path	e.g. /api/users, /api/orders/:id
HTTP method	GET, POST, PUT, DELETE, PATCH
Controller/view	Source file handling this route
Module/app	Which NestJS module or Django app owns it
Auth required	Whether authentication/permissions are needed

For NestJS: extract from @Controller + @Get/@Post/@Put/@Delete decorators. For Django: extract from urls.py → urlpatterns and viewsets.py → router registrations.

3. Map Global Context

Before analyzing individual pages, capture:

• Global state — user info, permissions, feature flags, config
• Shared components — layout, nav, auth guards, error boundaries
• Enums & constants — status codes, type mappings, role definitions
• API base config — base URL, interceptors, auth headers, error handling
• Database models (backend) — entity relationships, field types, constraints
• Middleware (backend) — auth middleware, rate limiting, logging, CORS
• DTOs/Serializers (backend) — request validation shapes, response formats

These will be referenced throughout page/endpoint analysis.

---

Phase 2 — Page-by-Page Deep Analysis

Analyze every page in the inventory. Each page produces its own Markdown file.

Analysis Dimensions

For each page, answer:

A. Page Overview

• What does this page do? (one sentence)
• Where does it fit in the system?
• What scenario brings a user here?

B. Layout & Regions

• Major regions: search area, table, detail panel, action bar, tabs, etc.
• Spatial arrangement: top/bottom, left/right, nested

C. Field Inventory (core — be exhaustive)

For form pages, list every field:

Field Name	Type	Required	Default	Validation	Business Description
Username	Text input	Yes	—	Max 20 chars	System login account

For table/list pages, list:

• Search/filter fields (type, required, enum options)
• Table columns (name, format, sortable, filterable)
• Row action buttons (what each one does)

Field name extraction priority:

1. Hardcoded display text in code
2. i18n translation values
3. Component placeholder / label / title props
4. Variable names (last resort — provide reasonable display name)

D. Interaction Logic

Describe as "user action → system response":

[Action]     User clicks "Create"
[Response]   Modal opens with form fields: ...
[Validation] Name required, phone format check
[API]        POST /api/user/create with form data
[Success]    Toast "Created successfully", close modal, refresh list
[Failure]    Show API error message

Cover all interaction types:

• Page load / initialization (default queries, preloaded data)
• Search / filter / reset
• CRUD operations (create, read, update, delete)
• Table: pagination, sorting, row selection, bulk actions
• Form submission & validation
• Status transitions (e.g. approval flows: pending → approved → rejected)
• Import / export
• Field interdependencies (selecting value A changes options in field B)
• Permission controls (buttons/fields visible only to certain roles)
• Polling / auto-refresh / real-time updates

E. API Dependencies

Case 1: API is integrated (real HTTP calls in code)

API Name	Method	Path	Trigger	Key Params	Notes
Get users	GET	/api/user/list	Load, search	page, size, keyword	Paginated

Case 2: API not integrated (mock/hardcoded data)

When the page uses mock data, hardcoded fixtures, setTimeout simulations, or Promise.resolve() stubs — the API isn't real yet. Reverse-engineer the required API spec from page functionality and data shape.

For each needed API, document:

• Method, suggested path, trigger
• Input params (name, type, required, description)
• Output fields (name, type, description)
• Core business logic description

Detection signals:

• setTimeout / Promise.resolve() returning data → mock
• Data defined in component or *.mock.* files → mock
• Real HTTP calls (axios, fetch, service layer) with real paths → integrated
• __mocks__ directory → mock

F. Page Relationships

• Inbound: Which pages link here? What parameters do they pass?
• Outbound: Where can users navigate from here? What parameters?
• Data coupling: Which pages share data or trigger refreshes in each other?

---

Phase 3 — Generate Documentation

Output Structure

Create prd/ in project root (or user-specified directory):

prd/
├── README.md                     # System overview
├── pages/
│   ├── 01-user-mgmt-list.md      # One file per page
│   ├── 02-user-mgmt-detail.md
│   ├── 03-order-mgmt-list.md
│   └── ...
└── appendix/
    ├── enum-dictionary.md         # All enums, status codes, type mappings
    ├── page-relationships.md      # Navigation map between pages
    └── api-inventory.md           # Complete API reference

README.md Template

# [System Name] — Product Requirements Document

## System Overview
[2-3 paragraphs: what the system does, business context, primary users]

## Module Overview

| Module | Pages | Core Functionality |
|--------|-------|--------------------|
| User Management | User list, User detail, Role mgmt | CRUD users, assign roles and permissions |

## Page Inventory

| # | Page Name | Route | Module | Doc Link |
|---|-----------|-------|--------|----------|
| 1 | User List | /user/list | User Mgmt | [→](./pages/01-user-mgmt-list.md) |

## Global Notes

### Permission Model
[Summarize auth/role system if present in code]

### Common Interaction Patterns
[Global rules: all deletes require confirmation, lists default to created_at desc, etc.]

Per-Page Document Template

# [Page Name]

> **Route:** `/xxx/xxx`
> **Module:** [Module name]
> **Generated:** [Date]

## Overview
[2-3 sentences: core function and use case]

## Layout
[Region breakdown — text description or ASCII diagram]

## Fields

### [Region: e.g. "Search Filters"]
| Field | Type | Required | Options / Enum | Default | Notes |
|-------|------|----------|---------------|---------|-------|

### [Region: e.g. "Data Table"]
| Column | Format | Sortable | Filterable | Notes |
|--------|--------|----------|-----------|-------|

### [Region: e.g. "Actions"]
| Button | Visibility Condition | Behavior |
|--------|---------------------|----------|

## Interactions

### Page Load
[What happens on mount]

### [Scenario: e.g. "Search"]
- **Trigger:** [User action]
- **Behavior:** [System response]
- **Special rules:** [If any]

### [Scenario: e.g. "Create"]
- **Trigger:** ...
- **Modal/drawer content:** [Fields and logic inside]
- **Validation:** ...
- **On success:** ...

## API Dependencies

| API | Method | Path | Trigger | Notes |
|-----|--------|------|---------|-------|
| ... | ... | ... | ... | ... |

## Page Relationships
- **From:** [Source pages + params]
- **To:** [Target pages + params]
- **Data coupling:** [Cross-page refresh triggers]

## Business Rules
[Anything that doesn't fit above]

---

Key Principles

1. Business Language First

Don't write "calls useState to manage loading state." Write "search button shows a spinner to prevent duplicate submissions."

Don't write "useEffect fetches on mount." Write "page automatically loads the first page of results on open."

Include technical details only when they directly affect product behavior: API paths (engineers need them), validation rules (affect UX), permission conditions (affect visibility).

2. Don't Miss Hidden Logic

Code contains logic PMs may not realize exists:

• Field interdependencies (type A shows field X; type B shows field Y)
• Conditional button visibility
• Data formatting (currency with 2 decimals, date formats, status label mappings)
• Default sort order and page size
• Debounce/throttle effects on user input
• Polling / auto-refresh intervals

3. Exhaustively List Enums

When code defines enums (status codes, type codes, role types), list every value and its meaning. These are often scattered across constants files, component valueEnum configs, or API response mappers.

4. Mark Uncertainty — Don't Guess

If a field or logic's business meaning can't be determined from code (e.g. abbreviated variable names, overly complex conditionals), mark it [TBC] and explain what you observed and why you're uncertain. Never fabricate business meaning.

5. Keep Page Files Self-Contained

Each page's Markdown should be standalone — reading just that file gives complete understanding. Use relative links when referencing other pages or appendix entries.

---

Page Type Strategies

Frontend Pages

Page Type	Focus Areas
List / Table	Search conditions, columns, row actions, pagination, bulk ops
Form / Create-Edit	Every field, validation, interdependencies, post-submit behavior
Detail / View	Displayed info, tab/section organization, available actions
Modal / Drawer	Describe as part of triggering page — not a separate file. But fully document content
Dashboard	Data cards, charts, metrics meaning, filter dimensions, refresh frequency

Backend Endpoints (NestJS / Django / Express)

Endpoint Type	Focus Areas
CRUD resource	All fields (from DTO/serializer), validation rules, permissions, pagination, filtering, sorting
Auth endpoints	Login/register flow, token format, refresh logic, password reset, OAuth providers
File upload	Accepted types, size limits, storage destination, processing pipeline
Webhook / event	Trigger conditions, payload shape, retry policy, idempotency
Background job	Trigger, schedule, input/output, failure handling, monitoring
Admin views (Django)	Registered models, list_display, search_fields, filters, inline models, custom actions

---

Execution Pacing

Large projects (>15 pages): Work in batches of 3-5 pages per module. Complete system overview + page inventory first. Output each batch for user review before proceeding.

Small projects (≤15 pages): Complete all analysis in one pass.

---

Common Pitfalls

Pitfall	Fix
Using component names as page names	UserManagementTable → "User Management List"
Skipping modals and drawers	They contain critical business logic — document fully
Missing i18n field names	Check translation files, not just component JSX
Ignoring dynamic route params	/order/:id = page requires an order ID to load
Forgetting permission controls	Document which roles see which buttons/pages
Assuming all APIs are real	Check for mock data patterns before documenting endpoints
Skipping Django admin customization	admin.py often contains critical business rules (list filters, custom actions, inlines)
Missing NestJS guards/pipes	@UseGuards, @UsePipes contain auth and validation logic that affects behavior
Ignoring database constraints	Model field constraints (unique, max_length, choices) are validation rules for the PRD
Overlooking middleware	Auth middleware, rate limiters, and CORS config define system-wide behavior

---

Tooling

Scripts

Script	Purpose	Usage
scripts/codebase_analyzer.py	Scan codebase → extract routes, APIs, models, enums, structure	python3 codebase_analyzer.py /path/to/project
scripts/prd_scaffolder.py	Generate PRD directory skeleton from analysis JSON	python3 prd_scaffolder.py analysis.json

Recommended workflow:

# 1. Analyze the project (JSON output — works for frontend, backend, or fullstack)
python3 scripts/codebase_analyzer.py /path/to/project -o analysis.json

# 2. Review the analysis (markdown summary)
python3 scripts/codebase_analyzer.py /path/to/project -f markdown

# 3. Scaffold the PRD directory with stubs
python3 scripts/prd_scaffolder.py analysis.json -o prd/ -n "My App"

# 4. Fill in TODO sections page-by-page using the SKILL.md workflow

Both scripts are stdlib-only — no pip install needed.

References

File	Contents
references/prd-quality-checklist.md	Validation checklist for completeness, accuracy, readability
references/framework-patterns.md	Framework-specific patterns for routes, state, APIs, forms, permissions

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Attribution

This skill was inspired by code-to-prd by @lihanglogan, who proposed the original concept and methodology in PR #368. The core three-phase workflow (global scan → page-by-page analysis → structured document generation) originated from that work. This version was rebuilt from scratch in English with added tooling (analysis scripts, scaffolder, framework reference, quality checklist).