Argus

The all-seeing, AI-powered SEO inspector.
A free Chrome extension + MCP server that brings enterprise-level SEO auditing to everyone — powered by Claude Opus 4.6.
getargus.app

Website · Chrome Web Store · npm · Features · Install · Opus 4.6 Integration · MCP Server · Architecture

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The Problem

Enterprise SEO tools cost $100-300/month. SEO expertise is locked behind years of specialist knowledge. Most free tools only scratch the surface.

Argus breaks these barriers. It's a completely free, open-source Chrome extension that gives you instant, deep SEO analysis on any webpage — powered by Claude Opus 4.6 for AI insights that rival expensive platforms.

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Features

Three-Tab Architecture

Extract — Every SEO tag at a glance

• Title, meta description, canonical, robots (with character count badges)
• Open Graph & Twitter Card tags with live social preview cards
• JSON-LD structured data with syntax highlighting and validation
• Heading hierarchy as a visual tree
• Link analysis (internal/external/nofollow counts)
• Image audit (missing alt text, dimensions, lazy loading, modern formats)
• One-click copy and full JSON/text export

Audit — 40+ rule-based SEO checks

• Weighted scoring (0-100) across 10 categories
• Categories: title, description, headings, images, links, technical, structured data, social, content, performance
• Color-coded severity (critical/warning/info/pass) with fix guidance
• Real Web Vitals: LCP, INP, CLS, TTFB via PerformanceObserver API

Insights — AI-powered deep analysis

• Three-tier AI provider system with automatic fallback
• Automatic page classification, content quality, and SEO strategy analysis
• On-demand: rewrite meta descriptions, improve titles, suggest FAQ schema, generate schema markup
• Opus 4.6 exclusive: SEO strategy brief, technical fixes, content gap analysis, competitor insights

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Opus 4.6 Integration

Argus uses Claude Opus 4.6 as its primary AI engine via a BYOK (Bring Your Own Key) architecture:

Three-Tier AI Provider System

Tier	Provider	How It Works
1 (Primary)	Claude Opus 4.6	User provides their API key (stored locally, never synced). Direct fetch() from the side panel to api.anthropic.com with streaming SSE.
2 (Fallback)	Gemini Nano	Chrome's on-device AI model. No API key, no network — runs locally.
3 (Always Available)	Static Analysis	Rule-based analysis — works offline with zero dependencies.

Opus 4.6 Exclusive Features

When Claude is configured, Argus unlocks advanced analysis that smaller models can't handle:

• SEO Strategy Brief — Comprehensive prioritized action plan analyzing ALL extracted data (meta, headings, links, images, schema, technical signals) plus audit results
• Schema Markup Generator — Generates complete, valid JSON-LD ready to paste into your page
• Technical Fix Generator — Produces exact HTML code fixes for every audit issue
• Content Gap Analysis — Identifies missing sections based on page type and heading structure
• Competitor Insights — E-E-A-T signals, featured snippet optimization, and advanced tactics

Why BYOK?

• Privacy — Your API key never leaves your browser (stored in chrome.storage.local)
• No backend — Direct browser-to-API calls, no proxy server
• No cost to us — Users control their own usage
• Graceful degradation — Works perfectly without any API key (Gemini Nano or static analysis)

API Architecture

Side Panel (React)
    │
    ├─ Has Claude key? → fetch('https://api.anthropic.com/v1/messages')
    │                     with streaming SSE, max_tokens: 2048
    │
    ├─ Gemini Nano available? → Chrome Built-in AI Prompt API (on-device)
    │
    └─ Neither? → Static rule-based analysis (always works)

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MCP Server — SEO Auditing in Your Terminal

Argus includes a Model Context Protocol (MCP) server that brings SEO auditing directly into Claude Code. Developers can audit any webpage's SEO without leaving their terminal.

Tools

Tool	Description
seo_audit	Full 40+ rule audit with weighted scoring
extract_meta	Extract all meta tags, OG, Twitter, JSON-LD, headings, links, images
compare_seo	Side-by-side comparison of 2-5 URLs
extract_json	Raw extraction + audit data as JSON for programmatic use

Setup

One-line install (recommended):

claude mcp add argus-seo -- npx -y @pixelesq/argus-mcp

Or build from source:

# Build the MCP server
cd mcp-server && npm install && npm run build

# Add to Claude Code
claude mcp add argus-seo -- node mcp-server/build/index.js

Or drop a .mcp.json in any project:

{
  "mcpServers": {
    "argus-seo": {
      "command": "node",
      "args": ["path/to/argus/mcp-server/build/index.js"]
    }
  }
}

Shared Audit Engine

The MCP server shares the same audit engine as the Chrome extension. The audit rules are pure functions that take a PageExtraction data structure — they work identically in both browser and Node.js runtimes.

Chrome Extension                    MCP Server
─────────────                       ──────────
content.ts (DOM APIs)               fetch() + cheerio (HTML parsing)
        ↓                                   ↓
   PageExtraction ◄───── SAME TYPE ─────► PageExtraction
        ↓                                   ↓
   auditors/engine.ts  ◄── SHARED CODE ──► auditors/engine.ts
        ↓                                   ↓
   AuditReport                          AuditReport (returned via MCP)

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Install

Chrome Extension

Quick install: Add to Chrome from the Chrome Web Store.

Or build from source:

1. Clone and build:

   git clone https://github.com/pixelesq/argus.git
   cd argus
   npm install
   npm run build
   

2. Open chrome://extensions/, enable Developer mode
3. Click Load unpacked, select .output/chrome-mv3
4. Click the Argus icon — the side panel opens

Configure AI (Optional)

Claude Opus 4.6: Click the gear icon in the Insights tab → enter your API key from console.anthropic.com

Gemini Nano: Requires Chrome 138+. Enable chrome://flags/#prompt-api-for-gemini-nano, restart Chrome.

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Architecture

Tech Stack

Layer	Technology
Extension Framework	WXT (Vite-based)
UI	React 19 + TailwindCSS 4
Language	TypeScript (strict)
Manifest	Chrome Extension Manifest V3
AI (Cloud)	Claude Opus 4.6 via Messages API
AI (On-Device)	Chrome Built-in AI (Gemini Nano)
MCP Server	@modelcontextprotocol/sdk + cheerio
Icons	Lucide React

Project Structure

argus/
├── entrypoints/              # Chrome extension entry points
│   ├── background.ts         # Service worker (side panel + headers)
│   ├── content.ts            # Content script (DOM extraction)
│   └── sidepanel/            # React side panel UI
│       ├── App.tsx
│       ├── tabs/             # Extract, Audit, Insights
│       └── components/       # UI components
├── lib/                      # Core business logic
│   ├── ai/                   # AI provider system
│   │   ├── claude.ts         # Claude Opus 4.6 API client
│   │   ├── gemini.ts         # Gemini Nano client
│   │   ├── provider.ts       # Unified provider with fallback
│   │   ├── prompts.ts        # System prompts (standard + Opus-enhanced)
│   │   └── settings.ts       # API key management
│   ├── auditors/             # Audit engine (shared with MCP)
│   │   ├── engine.ts         # Orchestration
│   │   ├── scoring.ts        # Weighted scoring algorithm
│   │   └── rules/            # 40+ audit rules across 10 categories
│   └── extractors/           # DOM-based data extraction
├── mcp-server/               # MCP server for Claude Code
│   ├── src/
│   │   ├── index.ts          # Server + tools
│   │   └── extractor.ts      # cheerio-based HTML extraction
│   └── package.json
└── .mcp.json                 # MCP config for Claude Code

Privacy

• No analytics, no tracking, no data collection
• The extension makes zero network requests except:
  1. (Optional) HEAD request for HTTP response headers
  2. (Optional) Claude API calls — only when user provides their own key, direct to Anthropic
• Gemini Nano runs entirely on-device
• API keys stored in chrome.storage.local (device-local, never synced)

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Development

# Extension dev server (hot reload)
npm run dev

# Production build
npm run build

# MCP server
cd mcp-server && npm install && npm run build

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License

MIT License — see LICENSE for details.

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_{Built for the Built with Opus 4.6: a Claude Code Hackathon}