How do I access textual information about an enemy?

The game says that each Eidolon has specific ways to defeat it. Also, in enemy information screens, there seems to be an area where text is supposed to be displayed but I can't see anything there. I tried this on multiple enemies (even used Libra several times on them) and I have checkmarks next to their names in the datalog but there doesn't seem to be anything.

Is there supposed to be additional information in the form of text or am I supposed to find it by trial and error?