A site that wants to let an AI agent act has a problem it rarely says out loud. It cannot tell which agent is actually at the door. A user-agent string is just text, and anything can send it. An IP range drifts as providers move their infrastructure around. So the site guesses, and the guess collapses into one of two bad defaults. Block too much, and the helpful agent never reaches the page. Trust too much, and anything wearing the right header walks straight in.
What the tag actually is
Web Bot Auth is the piece that removes the guess. It comes from active work at the IETF and is already in production at Cloudflare, and it lets an agent prove who it is on every request. The agent generates a signing key and publishes the public half at a fixed location, /.well-known/http-message-signatures-directory. It then signs each request it sends. The receiving site, or Cloudflare at its edge, checks that signature against the published key. A match is a verifiable claim about the sender. Copying the header does not reproduce it, because only the holder of the private key can sign.
Cloudflare calls the end-user-directed form of this a signed agent, and opened the program in August 2025 with a first cohort: ChatGPT agent, Goose, Browserbase, and Anchor Browser. The list lives in the public bots and agents directory on Cloudflare Radar, readable by anyone, customer or not. That public directory is the part that matters to me, because it makes the identity checkable by a third party instead of asserted by the agent itself.
