ActionController::ParamsWrapper

Wraps the parameters hash into a nested hash. This will allow clients to submit requests without having to specify any root elements.

This functionality is enabled in config/initializers/wrap_parameters.rb and can be customized.

You could also turn it on per controller by setting the format array to a non-empty array:

class UsersController < ApplicationController
  wrap_parameters format: [:json, :xml, :url_encoded_form, :multipart_form]
end

If you enable ParamsWrapper for :json format, instead of having to send JSON parameters like this:

{"user": {"name": "Konata"}}

You can send parameters like this:

{"name": "Konata"}

And it will be