sudo useradd -m [username] ?

su [username] ?

Or am I understanding your idea about switching context wrong?

This doesn't really when the CLI tool needs to access any data in your /home. There isn't a straightforward way using standard POSIX tools to share a directory with another user. (Of course it's possible, but it's not easy.)

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grosswait an hour ago | parent | next [-]

Then you set up a shared directory with common group permissions

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tempfile 2 hours ago | parent | prev [-]

If the CLI tool needs to access arbitrary data from your home directory, then it is you. There is no security boundary between you and another user with full access to everything you own.

If you want to share specific directories, you can just put the shared directory in a common location, set it to be owned by some group, and make both users a member of that group. I don't see anything not-straightforward in there?

	▲	delamon an hour ago \| parent [-]
		Or even use acl(5), which is simplier than making arbitrary groups.