We (Streak) are also the makers of the InboxSDK. We're planning on writing a post for how InboxSDK + Add-ons plays nicely together. Coming later today but in

We (Streak) are also the makers of the InboxSDK. We're planning on writing a post for how InboxSDK + Add-ons plays nicely together. Coming later today but in the meantime, tl;dr is we suggest having both if you're doing anything more than a sidebar. We (Streak) are doing both - to get more powerful API's on desktop but still having functionality on mobile.