where are the vagrant api docs?

Ruby has a comprehensive set of API docs, for example here.

Where are the API documents for Vagrant? The only thing I can find is the code, but that isn't a substitute for API documents.

What is vagrant box?

A Vagrant Box is a clone of a base operating system image. Using a clone speeds up the launching and provisioning process. 1. Instead of using the init command above, you can simply download and add a box with the command: vagrant box add ubuntu/trusty64. This downloads the box and stores it locally.

If you're looking for source code documentation, you can find it here:

http://rdoc.info/github/mitchellh/vagrant/frames

Anyway, Vagrant doesn't have a real API, but you can use machine readable output for interacting with it. More info here:

http://docs.vagrantup.com/v2/cli/machine-readable.html