This was voted deferred after a lengthy discussion: https://confluence.hl7.org/pages/viewpage.action?pageId=104565559#SMARTWebMessagingBallotReconciliationCC20210219-CapabilitiesandDiscovery   From the discussion: Proposal: We'll encourage implementers to use the new handshake protocol for detailed and contextually-aware discovery of what web messaging features an app is allowed to use. (We already have language to this effect.) We don't want to over-specify at this stage; providing more detail about discovery is a good target for a future SMW release, when we have some implementation experience to build on. 1) We should add to the handshake documentation a note that we are looking to standardize more of this behavior in a future release, based on implementation experience. 2) We should define a "smart-web-messaging" value that servers MAY include in their .well-known/smart-configuration file, within the "capabilities[]" array.  Future pull requests that implement these changes should be linked to this issue in the comments.