TagInfo is an app made by a chip manufacturing company called NXP. It does a decent job of determining the type of chip it’s talking to and fully scanning any accessible memory into a scan report. It also makes sharing information gathered easy, which makes diagnosing problems or answering questions about specific NFC tags one might have much more efficient.
Android
iPhone
Do note that iOS has some serious limitations still when it comes to NFC commands and communicating with tags, so TagInfo is far less informative on iOS than Android.