These are unimplemented metadata keywords and their use is currently a sort of no-op. However, this can cause bugs with different tooling: berkshelf/berkshelf#1404 It also is likely that whatever the user thinks the semantics should be eventually that some subset of users will guess incorrectly and get surprising behavior if we ever do implement these keywords. The proper approach to documenting optional cookbooks is currently via text in the README.md or a comment in the metadata.rb. The correct course of action in the future is that an RFC should be submitted to https://github.com/chef/chef-rfc to decide what the suggests and recommends semantics are, and to actually implement those semantics. Until then, users should avoid the use of these keywords (essentially they are 'reserved for future use' -- which means "do not use them now").