ssh on aws: Could not open a connection to your authentication agent

ssh on aws: Could not open a connection to your authentication agent

I am trying to add a key to an agent on an aws ec2 instance running
Ubuntu. The problem is I keep getting the "Could not open a connection to
your authentication agent" error.
I made sure that with
ps -e | grep [s]sh-agent
there were no agents running. Then I created an agent with
ssh-agent /bin/bash
(I also tried "eval ssh-agent" and "eval $(ssh-agent)", with no success
whatsoever).
When I tried to ssh-add a key, I get the "Could not open a connection to
your authentication agent" error.
I tried this as well (Could not open a connection to your authentication
agent).
Any ideas?