Best way to do a "your company" merge tag in Campaigns

Best way to do a "your company" merge tag in Campaigns

Hello! I want to be able to pull company information from my leads. This is what I have set up so far...

$[UD:COMPANY|your agency|]$

...but in the mails I'm sending to myself, it's only showing "your agency" not the company name associated with those email addresses. Can you only use merge tags for Contacts, not Leads?