tier 1Declared
The site says agents are welcome in its robots.txt. A permission, not a capability.
tier 2Probe-verified
We fetched the site and tested each signal ourselves. Dated, repeatable, re-checked on a schedule.
tier 3Behaviourally verified
An agent completed the action end to end — booked, bought, submitted — and it worked.
The five probe checks (tier 2)
Each is fetched live. A check passes only on a real response, never on a claim in a file. Since v1.1, markdown negotiation passes only when the body is markdown and differs from the HTML response — a text/markdown header on an HTML page does not count.
Markdown negotiationAccept: text/markdown
10,946 pass Markdown twin at a predictable URL/page.md
5,753 pass llms.txt/llms.txt
11,196 pass API catalogRFC 9727
5,442 pass MCP server answers/.well-known/mcp/server-card.json → tools/list
6,031 pass What the numbers do not mean
5,089 of the 10,946 sites that negotiate are on one documentation platform (Mintlify) that does it by default. That is evidence that the platform layer is moving, not 5,089 separate decisions; such sites are marked via mintlify on their report. 769 sites passed on the header but rate-limited the strict re-probe and are counted on the header until the next crawl. MCP is counted only where the server behind the card answered tools/list (or challenged for auth): 6,031 do; 2,830 cards point at nothing. Of the servers that answer, 5,070 are Mintlify's three-tool docs search and 311 are Teachify's course catalogue; 642 sites built their own. 437 sites that pass the probes but are parked pages or generated content are listed and never returned in results. Whether models read llms.txt in production is not something any provider has committed to; we test for it because it is cheap and coherent, not because it is proven to drive citations.
What is not in the results
Gambling and pharmacy sites are listed on the same terms as everything else when they are real businesses under a real jurisdiction; category finds candidates, hostname and country decide. Flags are reviewed by hand and re-checked every crawl. To dispute one: hello@knowngood.sh with the host.
abuse · excludedpirated streaming, ROM/APK downloads, rogue pharmacies, gambling affiliates and login mirrors, phishing-shaped sites
40 adult · excluded by defaultescort and adult directories; the pages still exist and are probed honestly
5 farm / parked · excludedgenerated content networks and domainer placeholders that pass every probe
25 platform_subdomain / platform_preview · listed, ranked last, not indexedtrial and preview deployments on a platform's free subdomain (*.mintlify.app etc.); the same product on its own domain ranks normally
367 Changelog
v1.1 · 2026-08-26378 www/apex host pairs collapsed to one report each. The host's own redirect or declared canonical decides; 18 pairs that express no preference keep both pages. Alias pages 301 to the canonical and leave the sitemap; the listed count falls accordingly.
v1.1 · 2026-08-26MCP re-graded strictly on all 8,955 card holders: card → initialize → tools/list. 2,645 non-working cards and 213 dead endpoints no longer count; tool names recorded and searchable; platform attribution (Mintlify, Teachify).
v1.1 · 2026-08-25Markdown negotiation re-graded strictly on all 11,348 header passes: markdown content-type, non-HTML body, body differs from the HTML response. 58 header-only passes (0.5%) removed; ~120 bot-challenge pages that had counted as passes removed. Platform attribution and parked/farm exclusion added.Rubric change: the September crawl scores both v1 and v1.1 so the trend stays comparable.
v1 · 2026-08Initial rubric. Five probe checks; tiers defined.
Method: about the index.