Google today announced the People API, a single API it hopes will eventually be able to replace both the existing Google+ APITrack this API and Google Contacts APITrack this API. The People API will allow developers to snag connection data from authenticated Google users with a single call, rather than multiple calls -- and that's good news for everyone.
As Google explains it, the People API will eclipse the Google+ and Contacts APIs because it uses the newest protocols and technologies. The Contacts API, for example, uses the somewhat dated GData protocol. The People API can reach into users' private contact lists (as long as permitted) to see if those contacts are linked to other, public profiles. Google says properly granted scopes will return results as a people.connections.list object, which can then be used to snag more data about the person in question. In other words, it will allow developers to connect more of the dots that exist between Google users.
The Google People API finds its foundation in HTTP and JSON, which means most any HTTP client can send requests and handle the response. There's a big if; applications must be properly authorized to access the API. Google isn't going to hand out this valuable data willy-nilly. Developers need to create projects via the Google Developers Console in order to gain the needed credentials. (More details on this available here.) Google also has a handful of tutorials, guides, and videos here to help get new developers up to speed on how to use Google APIs. Once developers have a chance to sign up and gain the necessary authorization, they'll be able to access user connections via the People API.
What's included in all this connection data? Plenty. For example, any social networks that users have given Google permisson to access will show up in their Google connection profile. Moreover, the People API exposes private addresses, phone numbers, emails, and birthdays (again, if permission is given by the users). Each person profiled will have their own resource_name, and more details for that individual can be gleaned from a simple People API call.
Google says the new People API should be able to help Web and mobile developers alike. It gently suggests developers use the API to "delight your users and those in their circles of influence." In other words, social apps should be able to do some creative things, but (please) don't be abusive.