Berks error regarding metadata.rb

Hi Everyone:

Chef newbie here. I'm working with chef cookbooks from marketplace. I'm just starting to use berks to download dependencies.

After using the knife site download cookbook command, I run a sudo berks init command and i get the following error:

The resource at ... does not appear to be a valid cookbook. Does it have a metadata.rb?

Any reason why it needs a metadata.rb file? There's already a metadata.json file in the cookbook I donwloaded. Should I simply create a metadata.rb file and type the dependencies in there?

thanks,

jon