API - get people who watch a ticket

I am currently trying to find a way to read the current subscribers of a particular ticket via API.

GET /api/v1/tickets/12345 gives me a lot of information about the ticket, but the mentions/watches are not listed.

GET /api/v1/mentions works more or less.
I first get a list of ALL mentions that exist, and then I can filter for the ticket based on the mentionable_id, and can then extract the user_id from it.

The problem with this is that it’s a rather unnecessarily large query, the number of tickets and resulting mentions keeps growing, so the output of /api/v1/mentions keeps getting longer and longer.

Is there any better way to take this off? Unfortunately I have not found one.