That looks good to me. I
think that, in the context of shells, "built-in" is an adjective and that, for the noun, you want "builtin"--but I am not 100% sure about this. It's what I write and what I usually read, though. Aside from that, you could make "shell builtin" (or "shell built-in") a link to the section in the Bash reference manual about shell builtins, or, if you prefer, some other source of documentation, such as some
Unix & Linux question about shell builtins.