Ok I’m not sure why this is working for me, but this is what I’m currently using and it appears to work. I’m on Big Sur with Spark v2.9.11 and Hook 2.0.3.
Get Name
tell application "Spark"
if HasSelectedMessage then
set theResult to GetSelectedMessageTitle
return theResult
end if
end tell
Get Address
tell application "Spark"
if HasSelectedMessage then
set theResult to GetSelectedMessageBacklink
return theResult
end if
end tell