57,266 websites an agent can use. Every one tested, every result dated.
Why this exists
AI agents now read websites and complete tasks on them for real people. Most sites cannot be read or acted on by an agent, and nothing told the agent which ones could. Known Good is that list. A site is listed because our probe connected to it and something answered; the date of that answer is on the listing.
What is in the index
57,266 websites are listed. Each listing says what the site offers an agent: a markdown version of its pages, a file of pages worth reading, a catalogue of its APIs, or a server an agent can call. The listing shows which checks passed, which failed, which could not be asked, and the day we asked. Search it at /, call it at /api/find, or connect an agent to it at /mcp.
How a site gets in
There are four routes, and placement is never one of them. A site publishes a file or endpoint meant for agents, which we treat as an invitation. A site appears in a public MCP or API registry. A listed site is checked again each pass. Or an owner asks at /submit. Consent gates every route: the probe reads the site's robots.txt first, and a no stops it. Every route ends at the same probe, under the same rubric. Nobody can pay to be listed, ranked, or kept.
How we test
The probe fetches a site's robots.txt first and stops if the answer is no. Then it reads the homepage and the well-known files the standards define, and knocks once on any server the site advertises, asking only for the list of tools. Nothing is bought, booked, or submitted. The rubric is published at /benchmark and the crawler's full behaviour at /bot. Results are read live from the site, not from a claim in a file.
The numbers, dated
The current index comes from a full pass run between 26 Sep 2026 and 28 Sep 2026, with a markdown re-check on 2 Oct 2026. 104,578 hosts were in scope. 95,529 hosts were asked. 606 hosts declined. 2,382 hosts could not be asked. 83,917 hosts had a valid door and were described. 57,266 hosts are listed. The probe made 2,149,241 requests in all, at most one at a time to any server. 13,284 domains came from public registries.
A host that could not be asked is never recorded as having failed.
What Known Good does itself
This site serves everything it tests for: markdown on request, a markdown twin of every page, /llms.txt, an API catalogue, an OpenAPI document, an MCP server, WebMCP tools in the page, and an agent card. If a check on this site ever fails, it fails in public like everyone else's.
For site owners
Your report page says what an agent found, what it could not find, and the smallest fix that changes the result. Request a probe at /submit if your site is not listed. Book a free 30-minute review at cal.com/knowngood.sh/30min and we will walk through your report with you.