ssh-add

ssh-add has a few decent options available, some of which are handy to know about.

-l will allow you to see loaded identities, along with their fingerprints:

[vagrant@centos1 ~]$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)

-D will allow you to remove all identities (and -d can be used to remove specific ones):

[vagrant@centos1 ~]$ ssh-add -D
All identities removed.

-x will lock an agent, while -X will unlock it:

[vagrant@centos1 ~]$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)
[vagrant@centos1 ~]$ ssh-add -x
Enter lock password: 
Again: 
Agent locked.
[vagrant@centos1 ~]$ ssh-add -l
The agent has no identities.
[vagrant@centos1 ~]$ ssh-add -X
Enter lock password: 
Agent unlocked.
[vagrant@centos1 ~]$ ssh-add -l
256 SHA256:P7FdkmbQQFoy37avbKBfzMpEhVUaBY0TljwYJyNxzUI vagrant@centos1 (ED25519)