I ran Brent Ozar's sp_blitz script, and one of the things it's complaining about is that my SQL Server Agent account has sysadmin permission. I removed the sysadmin permission, but then the agent wouldn't start. (See image below). There's nothing of note in the event log. When I restore the sysadmin permission the agent starts with no difficulty.
My account is a managed service account. None of the other managed service accounts I use (one for running reporting services, and one for running the SQL service) have sysadmin permission.
Is the sysadmin permission actually necessary? If not, what are the minimum permissions this account needs?