If you have spent the last year wiring an AI agent into anything, you already know the shape of the problem. Your agent does interesting things, and the protocol carrying its traffic does HTTP. The agent reasons about user goals, negotiates with other services, runs across sessions, takes actions on behalf of someone, and asks for permission to do things. The wire underneath sees a sequence of POSTs.
The Agent Transfer Protocol, AGTP, is a transport protocol designed for what agents actually do. It runs on its own port (4480, registered with IANA), uses TLS for confidentiality and authentication, and is being developed as an open standard at the IETF. The intent is the same intent SMTP had for email and DNS had for hosts: define a substrate that makes the job easier above it, and let the ecosystem build on top.
This post is a developer-level tour. Here is what AGTP does, what you get from using it, and how it fits with what you have already built.
Identity that lives on the wire
Every non-anonymous AGTP request carries a handful of mandatory headers, and they answer the questions intermediaries actually need to answer.
