Android Reverse Engineering & API Extraction

This skill provides a structured workflow to:

• decompile Android artifacts (APK/XAPK/JAR/AAR)
• trace call flows from entry points to network layers
• extract and document HTTP APIs (Retrofit endpoints, OkHttp calls, hardcoded URLs, auth patterns)

Prerequisites

• Java JDK 17+
• jadx (CLI)
• Optional (recommended): Vineflower/Fernflower, dex2jar

Workflow (high-level)

1. Decompile
   • Use jadx first for a broad pass (resources + sources)
   • Use Fernflower/Vineflower for better Java output on tricky code; compare when needed
2. Analyze structure
   • Identify launcher Activity, Application class, and DI setup
   • Map packages: api, network, data, repository, service, retrofit, http
3. Trace call flows
   • UI entry point → ViewModel/Presenter → Repository → API service → HTTP client call
4. Extract APIs
   • Retrofit: interface annotations (@GET, @POST, …)
   • OkHttp: Request.Builder, HttpUrl, interceptors
   • URLs: string literals (http://, https://) and base URL builders
5. Document endpoints

Use this template for each endpoint you discover:

### `METHOD /path`

- **Source**: `com.example.api.ApiService` (ApiService.java:42)
- **Base URL**: `https://api.example.com/v1`
- **Path params**: `id` (String)
- **Query params**: `page` (int), `limit` (int)
- **Headers**: `Authorization: Bearer <token>`
- **Request body**: `{ "email": "string", "password": "string" }`
- **Response**: `ApiResponse<User>`
- **Called from**: `LoginActivity → LoginViewModel → UserRepository → ApiService`

Notes

This repository also ships a Claude Code plugin implementation (scripts, references, and the /decompile slash command) under:

• plugins/android-reverse-engineering/