Being able to provide different levels of access for a single API has been one of the telltale characteristics of any modern web API. Savvy API providers know they don't just make their valuable API resources publicly available for anyone to use, they know you can craft a logical set of plans that are in alignment with your wider business objectives, outlining how any developer can put an API to use — this is the essential business of APIs.
Mashery was the first API management provider to standardize this approach to API access, something further evolved by 3Scale, Apigee, and others. Amazon's release of their API Gateway wove API management into the fabric of what we call the cloud, and the introduction of usage plans, does the same for API service composition. Making the identification, metering, limiting, and monetization of resources made available via APIs, a default function of operations in the cloud.
Being able to take any digital asset, whether it is data, content, or an algorithmic resource, and make available via a URL, and control who has access, while also metering their usage, and charging different rates for this usage, is where the business of APIs rubber meets the road. API service composition lets you dial in exactly the right levels of access, and usage, required to fulfill a business contract, delivering precisely the service that customers are wanting for their web, mobile, and device apps.
It's taken a decade for this key element of doing business on the web to mature beyond just a handful of vendors, then into an assortment of open source solutions, and now something that is just baked into what we know as the cloud — allowing us to plan API access consistently and universally across all the digital resources we are increasingly storing and operating in the cloud.