web-api-analyzer

name	web-api-analyzer
description	Analyze website API endpoints and JS logic using Playwright. Intercept network requests, extract API patterns, capture encrypted parameters, and export HAR files. Use when the user wants to reverse-engineer a website's API calls, analyze request/response patterns, or understand JS encryption logic.
metadata	{"requirements":{"bins":["node"],"npm":["playwright"]}}

Web API Analyzer

A Playwright-based tool for intercepting and analyzing website API calls and JS logic.

Capabilities

1. Network Interception — Capture all XHR/Fetch API requests with full headers, params, and response bodies
2. API Pattern Extraction — Auto-identify API endpoints, auth methods, and request patterns
3. JS Analysis — Inject JS to hook crypto functions (e.g., encrypt, sign, md5), intercept XMLHttpRequest and fetch
4. HAR Export — Save full network traffic as HAR for further analysis
5. Cookie/Token Tracking — Track auth tokens, cookies, and session changes

Usage

1. Basic API Capture

Capture all API requests from a URL:

node <skill_dir>/scripts/capture.cjs --url "https://example.com" --duration 15000 --output /tmp/api-capture.cjson

Options:

• --url (required): Target URL
• --duration: How long to capture in ms (default: 10000)
• --output: Output file path (default: stdout as JSON)
• --har: Export as HAR format instead of JSON
• --filter: Regex to filter URLs (e.g., --filter "api|ajax")
• --click: CSS selector to click after page load (triggers more API calls)
• --scroll: Auto-scroll the page to trigger lazy-load APIs
• --headers: Show full request/response headers
• --body: Capture response bodies (can be large)
• --cookie: Include cookies in output

2. JS Hook Analysis

Inject hooks to monitor JS crypto/encoding functions:

node <skill_dir>/scripts/js-hook.cjs --url "https://example.com" --hook crypto --duration 15000

Hook types:

• crypto — Hook Web Crypto API, CryptoJS, JSEncrypt, md5, etc.
• fetch — Hook fetch() and XMLHttpRequest with full params
• storage — Hook localStorage/sessionStorage access
• cookie — Hook document.cookie read/write
• all — All of the above

3. Interactive Analysis

For complex sites, use the interactive mode which opens a headed browser:

node <skill_dir>/scripts/capture.cjs --url "https://example.com" --headed --duration 60000

This allows manual interaction while all network traffic is captured.

Workflow

1. Start with basic capture to see all API endpoints
2. Identify interesting endpoints (auth, data, search)
3. Use JS hooks to understand encryption/signing logic
4. Reconstruct the API call independently

Output Format (JSON)

{
  "url": "https://example.com",
  "timestamp": "2025-01-01T00:00:00Z",
  "requests": [
    {
      "url": "https://api.example.com/v1/data",
      "method": "POST",
      "headers": { ... },
      "postData": "...",
      "response": {
        "status": 200,
        "headers": { ... },
        "body": "..."
      },
      "timing": { "start": 0, "duration": 123 }
    }
  ],
  "cookies": [...],
  "jsHooks": [...]
}