An agent needs to have a directory dedicated to Jenkins. Specify the path of this work directory on the agent. It is best to use an absolute path, such as '/var/jenkins' or 'c:\jenkins'. This should be a path local to the agent machine. There's no need for this path to be visible from the master, under normal circumstances.

Agents do not maintain important data (other than active workspaces of projects last built on it), so you can possibly set the agent workspace to a temporary directory. The only downside of doing this is that you may lose the up-to-date workspace if the agent is turned off.

If you use a relative path, such as './jenkins-slave', the path will be relative to the current working directory that the launcher provides.