I have a database table comprised of census data that gives a 12 digit FIPS code that refers to the census block. I need to cross reference this data with another table that provides latitude and longitude. I would like to convert the 12 digit FIPS code to GPS coordinates (either a centroid, or the bounds of the tract).

I have found reference to an API provided by the Census Bureau here, but I can't seem to find the actual documentation for that API.

A similar question has been asked here, but I would prefer to use an API if possible.