> It'll automatically add keys to your agent the first time you use them during a session
If you have more than one private key in your agent, then SSH will try each one sequentially. That can lead to mistakenly getting banned by monitoring software for what can appear indistinguishable to be an authentication attack. Not to mention the wrongness of presenting "any and all keys" to any host you connect to.
If you have multiple keys in your agent, you _really_ should manually configure what key to present using `-i` or `IdentityFile`. But you should also use `IdentitiesOnly` too.
If you have more than one private key in your agent, then SSH will try each one sequentially. That can lead to mistakenly getting banned by monitoring software for what can appear indistinguishable to be an authentication attack. Not to mention the wrongness of presenting "any and all keys" to any host you connect to.
If you have multiple keys in your agent, you _really_ should manually configure what key to present using `-i` or `IdentityFile`. But you should also use `IdentitiesOnly` too.