SEO Notary

Verify what a web page really returns, so your coding agent can fix it and prove it.

HTTP and real-browser checks for Claude Code, Cursor, VS Code and CI. Deterministic. No LLM. One command.

Status: 0.1 (early release). APIs, rule output and rule severities may still change between 0.x releases; see the changelog.

Coding agents edit page code but cannot see what the page actually serves. Client-side scripts overwrite titles and canonicals, server rendering breaks, redirects bounce, and the agent reports “done” without evidence. SEO Notary fetches the page, runs deterministic rules over the response and the rendered DOM, and returns structured findings with stable exit codes.

$ seo-notary verify http://127.0.0.1:4173/broken --tier browser
FAIL http://127.0.0.1:4173/broken
tier browser (faithful), 1153 ms, 0 redirects, HTTP 200
  title        Acme Widgets | Handmade widgets for every workshop
  canonical    http://127.0.0.1:4173/broken
  rendered DOM
  title        Loading...
  canonical    https://staging.acme.example/broken

2 errors, 0 warnings, 0 info; 20 rules passed

ERROR   RENDER_TITLE_DIFFERS  head > title
  The title changes after JavaScript runs.
  raw:      Acme Widgets | Handmade widgets for every workshop
  rendered: Loading...
  fix: Make the server-rendered title and the client-rendered title agree.
$ echo $?
1

That output is abridged from a real run of the demo in this repository. Remove the script that rewrites the title and canonical and the same command prints PASS and exits 0.

Quickstart

Requires Node >=22.19.0.

# Tier 1: raw HTTP and HTML. No browser, nothing to download.
npx seo-notary verify http://localhost:3000/

# Tier 2: also render the page in Chromium and compare raw vs rendered.
npx seo-notary install-browser
npx seo-notary verify http://localhost:3000/ --tier browser

To run from a checkout instead: npm install && npm run build, then node packages/cli/dist/bin.js verify .

Exit codes: 0 pass, 1 findings at or above --fail-on (default error), 2 operational failure (bad input, network, timeout, policy, browser). Use --format json for exactly one JSON document on stdout. Details: docs/CLI.md.

Use it from an agent

seo-notary mcp runs a local MCP server over stdio with two tools: verify_url and get_rule_catalog. verify_url returns the full report as structured content plus a short summary, in one call. See docs/MCP.md for what has and has not been tested, and for an AGENTS.md snippet that tells agents to verify after frontend changes.

What it checks