AI Product Index / Web Bot Auth key directory
It lets you tell a real signed agent from anything that copied its user-agent string, and it lets callers verify your responses. The infrastructure side of agent traffic rather than the content side.
Publish Ed25519 keys at /.well-known/http-message-signatures-directory (RFC 9421 web-bot-auth) so callers can verify your responses, and so you can tell a signed agent from an anonymous scraper.
Free, no signup, same endpoint that produced every grade on the leaderboard:
curl "https://index.percall.dev/api/score?url=https://your-site.example"
It returns the letter grade and every check by name with pass/fail. The
$0.05 call at POST /api/audit adds why each one failed and a
snippet with your origin already in it.