It's not for JSON transformation directly, but a nice package by @Guillaume Rongier that lets you have messages contain data in JSON vs XML in the Interoperability pipeline.

Hi @Dmitrij Vladimirov ! This is pure ObjectScript AFAIK in an expression mode (think of it if you create a classmethod in ObjectScript in Expression mode), with options of %source to reference base class properties and %cube to reference Cube class methods.

BTW, faced the same situation today to have an option of getting full sqlname for a class, and generated a classmethod in VSCode with AI (no my personal touch):

ClassMethod GetSQLTableName(pclass As %String) As %String
{
// returns the SQL table name for a class
set tablename = ##class(%DeepSee.Utils).%GetSQLTableName(pclass)
if tablename="" {
set tablename=$TR($P(pclass,".",1,*-1),".","_")_"."_$p(pclass,".",*)
}
return tablename
}

And its working. Not bad for a bot.