ssh-agent - use specific key for specific hosts

Using 1Password SSH keys has worked fine until I crossed a threshold in the number of keys whereby some hosts don't like how many keys they are offered. I found this old thread that describes how to customize the agent.toml file to indicate which keys are presented, but that doesn't really help when I have a number of vault keys I need to use. I could resequence them using agent.toml, but I'll just have this same problem with one host or another.

I basically need to somehow map prevent ssh-agent from scouring the entire list. The thread above indicated that there would be future work on this - it might be that I'm just asking for an update.