For convenience, you can also use pname and version attributes and mkDerivation will automatically set name to "${pname}-${version}" by default.
The error messages are not helpful when one messes up the input attribute set ofmkDerivation (i.e., either name, or pname and version attributes have to be present); see Nixpkgs issue #113520.
6.1. Using stdenv
The function mkDerivation in the Nixpkgs standard environment is a wrapper around derivation that adds a default value for system and always uses Bash as the builder, to which the supplied builder is passed as a command-line argument. See the Nixpkgs manual for details.
"Documented" in the Nixpkgs manual under 6.1 Using stdenv.
Used the double-quotes above because I don't consider it well documted. Will give it a try too; worst case scenario is that I'll fail as well.