First, my apologies for the slow response - I didn't get my typical email saying there was a post in the forum. Anyway...
SN2Info API may meet some of your needs. It will return some contract details, such as contract number and service line end date for a particular device (assuming the requester is entitled to the data of course). But it is based on a serial number and not a contract.
I am unaware of a contract-based API available today. I understand SNTC team is working on APIs that access the portal data and those APIs may include contract info. There also may be something available in CCW-R (the replacement for CSCC), but I don't know for sure.