Congratulations to the RFC authors (Richard Barnes, @jsha, @cpu, and @jdkasten) on the issuance by IETF today of the Proposed Standard RFC for the ACME protocol!
https://www.rfc-editor.org/info/rfc8555
This document represents literally years of design work and negotiation at Let’s Encrypt and within the IETF process and provides a great foundation for interoperability between client tools and certificate authorities.