The Nylas Node.js Sample Code demonstrates how to use the SDK to access the API. The Nylas Communications Platform allows developers to build features that connect to every inbox, calendar, and contacts book.
FullContact has announced the CardShark API. The CardShark API allows users to "to send images of business cards to FullContact, and...receive back a response containing transcribed structured contact data." The advantage the API method of optical character recognition over competitors lies in the ability to send contacts to devices and applications beyond the device that captured the initial picture.
Google Contacts API gives client applications access to a user’s contacts list where the application can create new contacts, update or delete existing ones, or query for contacts that match particular criteria. This tutorial explains how to implement the API in C# and ASP.NET with OAuth 2.0.