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HAR-MCP

Capture any website's traffic and reverse-engineer its APIs. One prompt = full audit + API docs + code snippets.

What it does

An AI assistant connects to this MCP server and gets 20 tools to:

  • Capture HAR from any URL via headless Chromium

  • Audit performance, security headers, payloads, trackers, best practices

  • Reverse-engineer APIs — discover hidden endpoints, extract auth, generate OpenAPI specs

  • Generate code — Python, curl, JS snippets for every discovered endpoint

  • Visualize — waterfall charts, audit reports, Swagger-like API docs

Related MCP server: mcp-network-analyzer

Setup

python3 -m venv .venv
source .venv/bin/activate
pip install playwright fastmcp pyyaml pytest
playwright install chromium

Run the server

python -m har_mcp.server
# Runs at http://localhost:8000/sse

Connect to your LLM

Add to your MCP config:

{
  "mcpServers": {
    "har-mcp": {
      "type": "sse",
      "url": "http://localhost:8000/sse"
    }
  }
}

All 20 MCP Tools

Capture

Tool

What it does

capture_har_tool

Capture HAR from a URL using headless browser

Performance & Security Audit

Tool

What it does

audit_website

One-shot full audit — capture + all analyses + HTML report

analyze_performance_tool

0-100 performance score with breakdown

find_slow_requests_tool

Find requests slower than threshold

find_failed_requests_tool

Find HTTP errors (4xx/5xx)

list_endpoints_tool

All endpoints with counts and avg duration

check_security_headers_tool

Missing CSP, HSTS, X-Frame-Options, etc.

find_large_payloads_tool

Find bloated responses

find_redirect_chains_tool

Detect redirect chains

find_third_party_requests_tool

Detect trackers and ad scripts

check_best_practices_tool

Caching, compression, render-blocking checks

compare_hars_tool

Compare two captures (before/after)

generate_waterfall_tool

HTML waterfall chart

generate_report_tool

Full HTML audit report

API Reverse Engineering

Tool

What it does

reverse_engineer_site

One-shot — capture + discover APIs + generate docs

discover_apis_tool

Find all hidden API endpoints from traffic

detect_auth_patterns_tool

Detect JWT, API keys, cookies, OAuth flows

generate_openapi_spec_tool

Generate OpenAPI 3.0 YAML (import into Postman/Swagger)

generate_code_snippets_tool

Python, curl, JS code for every endpoint

generate_api_docs_tool

Interactive Swagger-like HTML documentation

Example Prompts

The killer demos:

"Reverse-engineer the APIs for https://some-site.com"

Captures the site, discovers all API endpoints, detects auth patterns, generates an OpenAPI spec, code snippets, and interactive API docs.

"Audit https://some-site.com"

Full performance + security + best-practices audit with HTML report.

Specific questions:

"What APIs does this site use?" "Show me the auth patterns" "Generate a Swagger spec from this site" "Give me Python code to call their search API" "What trackers does this site have?" "Compare these two captures"

Run tests

pytest tests/ -v
# 53 passed

Project structure

har_mcp/
├── server.py          # MCP server — 20 tools over HTTP/SSE
├── capture.py         # Playwright HAR capture
├── analyzer.py        # Performance, security, best practices analysis
├── api_discovery.py   # API reverse engineering engine
├── visualizer.py      # Waterfall chart + audit report + API docs
├── models.py          # Data models
├── config.py          # Configuration
├── utils.py           # Helpers
tests/
├── sample.har         # Rich test fixture (19 entries with APIs, auth, GraphQL)
├── test_analyzer.py
├── test_api_discovery.py
├── test_capture.py
├── test_visualizer.py

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