I have two private ssh keys : one to access my personnal machines, one to access servers at my job. I add those two keys to my ssh-agent with ssh-add. Now, when I do ssh -A root@jobsrv I would like to forward agent authentication only for my job key (the one I'm using to connect jobsrv). I want this because anyone having root access to jobsrv can use my agent to authenticate himself to my personnal machines. Is there a way to achieve this isolation? 
ssh-agent: don't forward authentication for the whole keyring
ssh;security;ssh agent
Unfortunately, I believe it is not possible to achive this easily at the present moment. One could use two agents (one for each key) so that there is no agent holding every keys. But this would be pretty cumbersome to work with. This is why a bug report (enhancement) has been opened. There is this similar report too.  