The objective of this deliverable is to describe the development of the API, which will be based on different HYPERGRYD tools/service requirements regarding data exchange needs, formats, etc.,successfully integrating tools and services developed by the project partners - Gussing Energy Technologies Gmbh (GET), Encoord GmbH (ENCO), Grid Singularity (GSY), and Kungliga Tekniska Hoegskolan (KTH) - into the HYPERGRYD PaaS/SaaS developed by project partner IDP Ingenieria Y Arquitectura Iberia SL (IDP). The API, which underpins HYPERGRYD’s PaaS and its integrated services/tools aims to take into account end-user/stakeholder recommendations, usability techniques and methods - used at different stages of the development - which guarantees an end product that meets previous needs and requirements from stakeholders, use cases, roles, ICT architecture, planning platform and data requirements.