SQL Server Agent fails to start because of the error 15281 is a very common error.
When you start to restart SQL Agent sometimes it will give following error.
SQL Server blocked access to procedure ‘dbo.sp_get_sqlagent_properties’ of component ‘Agent XPs’ because this component is turned off as part of the security configuration for this server. A system administrator can enable the use of ‘Agent XPs’ by using sp_configure. For more information about enabling ‘Agent XPs’, search for ‘Agent XPs’ in SQL Server Books Online. (Microsoft SQL Server, Error: 15281)
To resolve this error, following script has to be executed on the server.
sp_configure 'show advanced options', 1;
sp_configure 'Agent XPs', 1;
When you run above script, it will give a very similar output as following on the screen.
Now, if you try to restart SQL Agent it will just work fine.
That’s it! Sometimes there is a simpler solution to complicated error.
Reference: Pinal Dave (http://blog.sqlauthority.com)