Sierra's agent protocol lets a visit start as a guest. Write the guest tier first.

Sierra's Oct 9 draft of the Personal Agent Protocol lets an agent start a visit as a guest, so I'd write the guest tier first. Bret Taylor and Clay Bavor, Sierra's co-founders, laid it out in Sierra's Oct 9, 2026 post. They call it Poppy, and they named 35 more design partners. A company posts one file at /.well-known/poppy.json. The agent says who it's acting for. Sign-in runs on OAuth, and the token carries only the access the customer approved. The company picks the channel: its pages, its APIs over OpenAPI or MCP, or its own agent.

Here's what I'd do on a software company's site. List what a guest agent can read today: pricing, docs, the security page. Write those answers so they survive being quoted, because they will be. Keep the signed-in list short, like starting a trial or changing a plan. A buyer who sends an agent to your pricing page is still a buyer doing research, and the answer it carries home is your first pitch.