So I created a magic item that uses the tooltip to display sending as a link and it works while I'm in the homebrew creations screen. However when I switch to my character sheet to see if it works properly it displays in the equipment as [ spell]sending[/ spell] (without the spaces in the [ ])

I compared it with an official magic item (staff of defense) and the format looks the same but in equipment it shows as normal text 

Edit; Never mind, I had put spaces between the [ ] tags and the text inside them. I think it just needed some time to refresh the system