Note that if you want to use the command-line program (agda), then
you should also install the Agda-executable package. The Agda
package includes an Emacs mode for Agda, but you need to set up the
Emacs mode yourself (for instance by running agda-mode setup; see
the README).

Note also that this library does not follow the package versioning
policy, because the library is only intended to be used by the Emacs
mode and the Agda-executable package.