"A good API makes it easier to develop a program by providing building blocks. A programmer then puts the blocks together."
An API is a structured way to engage with NASA data. Without it, most data sets are effectively unusable by third-party developers -- the fixed cost of data wrangling is too high.
"Most important element for NASA data science? Making the data usable." DJ Patil
If a data set is created in the woods and no one uses it, is it data? No.
(Now.)