%BuildIndices is required if the indexed values are manipulated directly in the Global.
OR if the index definition is changed in Class or By DDL
during use as Object or SQL table it is maintained automatically.

• for a NEW created index this is "work in progress" that shouldn't be used until completed.
• if it's a matter of repair  $SYSTEM.OBJ.ValidateIndices() might be more useful. see my article Fix broken index 

Hi @Ben Spead !
My personal congratulations to see you here!
Working with you and your team on the worldwide HERMES project was one
of my highlights during my time at InterSystems.
It was due to your interpersonal skills to make this team so successful.

It was so special to me to participate and share this experience.
As a Sales Engineer with no local office I often felt "at the outer border of the milky way".
Not lost in space but almost.
But working in your team gave me the feeling of a "technical home".
As Engineer I enjoyed to style and create a product.
Which was more important to me than to consult, advice, and teach how to use some features.

Big THANKS for that!

Robert