No Tools is a fairly simple terminal challenge, something for new players to chew on.
I suspect there are several different ways to solve it, but the basic idea is to read a file using only built-in functions from sh.
I personally solved it with the read built-in:
$ read FLAG < /home/ctf/flag.txt && echo $FLAG
CTF{where-are-my-tools}
Another solution that my co-organizer developed used exec:
$ exec < /home/ctf/flag.txt
$ /bin/sh: 2: CTF{where-are-my-tools}: not found