g.command 'unfurl' do |c|
          c.flag 'channel', desc: 'Channel ID of the message. Both channel and ts must be provided together, or unfurl_id and source must be provided together.'
          c.flag 'ts', desc: 'Timestamp of the message to add unfurl behavior to.'
          c.flag 'unfurls', desc: 'URL-encoded JSON map with keys set to URLs featured in the the message, pointing to their unfurl blocks or message attachments.'
          c.flag 'source', desc: 'The source of the link to unfurl. The source may either be composer, when the link is inside the message composer, or conversations_history, when the link has been posted to a conversation.'