Nowadays, the proliferation of cloud-based services has revolutionised the way people communicate, connect, share and eventually conduct business. Thus, businesses conducted both by huge or small and medium enterprises are forced into providing their core competence(value) through an API. The OPENi approach(http://www.openi-ict.eu/) aims at analysing and classifying into categories the landscape of existing cloud-based services today and their publicly available APIs. Through multiple iterative steps, a map of cloud-based services along with multiple dimensions has been designed and an in-depth analysis of the selected set of APIs has been conducted. A set of Generic APIs (together with their associated objects, functionalities and relations to existing cloud-based services) are proposed, abstracting functionality for several popular categories of existing cloud-based services which bind to multiple service providers. In order to make those mappings interoperable and extensive a graph modelling was proposed by mapping the Generic APIs to the schema.org vocabulary. Furthermore, one additional tool is presented, he API Builder (http://api-builder.tools.epu.ntua.gr/web/) which is a community-based platform that aims to facilitate enterprises in adopting a Graph API that unifies the experience of multiple cloud-based services APIs and personal cloudlets, building and maintaining their software applications easily, despite any changes made in the CBS APIs. Following the aforementioned discussion, we briefly describe a novel approach to enrich existing API standards with business rules. This aims into taking advantage of the REST principles to enable the creation of generic clients that can operate as Finite State Machines and autonomously navigate through the vast semantically enriched web.