How to know what indexes a resource has before purchase?
Ask.
It's absolutely critical that after months and months of 'In Development' to sell the hard work as 'We did something.' (Various levels of something.)
I do not understand FL marketing. My first purchase in 2005 was a bet they did 'something'. My bet was successful (no thanks to 'marketing').
The index for most books should be obvious/described in the product page e.g. lexicons, commentaries, encyclopedia, bible dictionary. FL are known to make mistakes, so you can return within 30 days or create a metadata bug report in the General forum.
What causes you to ask the question?
Obviouness of indices? In Hermeneia, is Q indexed, and which was used? How do the OT commentary indices differ. For a DSS resource, which indices were used? And ancient, ANET, COS or specialized? Or even indexed?
Then, there's tagging.
Product pages are less helpful than even Amazon.
