On the geo-spatial operator documentation like http://docs.mongodb.org/manual/reference/operator/query/box/#op._S_box. It is not very clear and explicit on what absolute list of geo-indices support that operator.

On the $box documentation page mentioned here, it says "The query calculates distances using flat (planar) geometry. The 2d geospatial index supports the $box operator." This leaves it open to interpretation if any other indices support this operator?

It may be be useful to explicitly say that "only 2d geospatial index supports ..." instead of leaving it to users to assume that there is some implicit assumption in that sentence.

The same is true for all other geo-spatial operators.