Warp Sense

You attune your senses to detect a faint shimmering around any portals within a 60-ft radius of yourself. As an action, you can focus your senses on a known portal to deduce which plane it leads to, the type of portal (conditional, one-way, permanent, shifting, or variable), and what the portal’s key is (if any).

Source: The Infinite Planes Player's Companion by Aaron Infante-Levy