Firstly, Haystack is designed to sync your Haystack contacts into your contacts app, rather than being your 'contacts app'. This said, we do have a feature for importing your phone's contacts into Haystack. This article explains how.
The key advantage of syncing your Haystack contacts into your phone, is that the contacts app on your phone is where all your contacts live, so it would normally make sense to sync your Haystack contacts too.
Another advantage of Haystack contacts is that they are SMART. They are smart, because when our learning system knows of updates to these contacts, it will automatically update your local contacts on your phone (no more outdated contacts!).
Some users may want to import their phone's contacts into Haystack, so these contacts become 'smart' too.
To 'sync your phone contacts' into Haystack:
In the Haystack app, go to the 'settings' screen (bottom right on iOS, or top left on Android)
Tap the 'search my phone's contacts' option and follow the prompts
Haystack's search function will NOT import all your contacts. It searches your phone's contacts to find which of your contacts are on Haystack. Once it finds the relevant contacts, Haystack uploads their information to Haystack's servers, works its magic, and then syncs the smart contact back to your device.
For privacy reasons, Haystack does not upload any of your contacts which it cannot augment in any way.