autocomplete-ruby-rct is Ruby completion package based on rcodetools.
This package depends on rcodetools. You have to install it.
For example:
$ gem install rcodetools
If you use this on Windows, you may need to install forked rcodetools.
$ gem install specific_install
$ gem specific_install -l https://github.com/rcodetools/rcodetools.git
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.