I don't think what you are expecting is even possible, at least not for the average Joe at home.
First off you don't calculate a person's credit score. Credit recording agencies do that and report a score to authorized businesses such as banks. An individual has to sign a release of that information to the business granting the credit reporting agency permission to release the data. After all it is your private credit history; not just anyone can ask to see it.
There are a couple
developer interfaces (API's) for writting software for banks and other bonded companies. But the information is not free. It requires the company to be a subscriber to the reporting agency, licensed to receive the data and so on. Generally the developer never sees real live data. The API accesses dummy data so the developer can test their routines/programs/interfaces. The paying customer company pays for each and every 'live' record pulled.
Is your project a homework assignment for school, a project to build your skills, or is this a true enterprise project for your company?