Likely we have discrepancies right now as nothing has really checked compliance before.
Clients/tools
Runtimes (only listing known maintained ones)
On the client-side, like noflo-ui / fbp-spec etc, I think that flowbased/fbp-protocol-client#50 is the way to go. This will also give some tools for checking that the various runtimes are doing OK, and maybe provide some debugging help if things behave wierdly