publish gp service script to return geometry Json objects

[FangmingDu]

Hello Everyone,

I'm very new to ArcGIS-server restapi, but have been using ArcGIS desktop and other web maps for a while.

In one of the Buffering javascript api example (http://tasks.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer),
I found one GP service which takes geometres in as parameters and return buffered gemetries as JSon objects.

This seems to be very interesting to me. I'm thinking about writing another rest GP service myself, which can take a string parameter and create a bunch of gemetries as Json object. (The reason for that is I'm creating some spatial elements on the fly with users' request)

But it's very difficult even to find a place to start...
Should I write a python script which can return a Json object and then publish that script as a service?

If anyone can give me a hint on where to start, it would be much appreciated!!!

Thanks