The objective of the ATTEST project is to develop and operationalize a modular open source toolbox comprising a suite of innovative tools to support TSOs / DSOs operating, maintaining and planning the energy systems of 2030 and beyond in an optimised and coordinated manner, considering technical, economic and environmental aspects. The consortium, from six EU countries, that has been assembled to deliver ATTEST consists of five highly experienced research organisations in the energy systems area, two utilities that manage and operate the transmission system and the distribution system in Croatia, and two industry partners that specialise in the development of advanced ICT solutions and SCADA systems. The development of this broad spectrum of energy-related ICT tools and the utilization of next generation algorithms, demonstrated in a real world environment has not been attempted before. The outputs from the ATTEST project will enable accelerated dissemination, by a wide range of research institutions, within and outside of the project consortium, of the tools that will help TSOs and DSOs to better manage their networks. The demonstration of the results of the project will be valuable for the scientific community and EU energy industry and attest to the relevance of the solutions developed. The ATTEST’s ambition is to enable a wide range of users to utilize and test the tools developed in the project, thereby contributing to spread knowledge and experience in the energy systems community in the EU and on a global scale. This will contribute significantly to addressing not only the specific challenges of the call and the Horizon 2020 Energy Work Program, but also those of the EU’s Energy Union strategy and the 2020 Climate & Energy package.