Claude SEO is a free, open‑source plugin for Claude Code that performs a comprehensive SEO audit of any website in roughly ten to fifteen minutes by launching up to seventeen parallel specialist agents drawn from a pool of twenty‑six sub‑skills and nineteen agents, each modeled on Sonnet or Opus. The audit runs inside an isolated Python 3.11‑3.14 environment with a headless Chromium browser created by the /seo setup command, which prepares the runtime without affecting the host system. It evaluates technical SEO (crawlability, indexing, sitemaps, robots.txt, redirects, page‑speed and Core Web Vitals), content quality (E‑E‑A‑T, thin pages, topic coverage), structured data (Schema.org detection, validation and generation), AI‑search readiness (Google AI Overviews, ChatGPT, Perplexity, Gemini, and other generative engines), and local/e‑commerce signals (Google Business Profile, reviews, map pack, product pages). Findings are scored, sorted by impact and returned as a prioritized action plan in Markdown, JSON or PDF, with each recommendation explaining its basis, dependencies and verification method. The tool requires Claude Code 1.0.33+ and can connect optional free Google APIs for real field data, but operates without any paid credentials. Installation is performed via git clone or a marketplace plugin, and the project reports 10.8 K Search Console clicks and a 99 mobile PageSpeed score after auditing its own site, illustrating its effectiveness.