The field of Global Mental Health (GMH) has made substantial progress in generating an evidence base, gaining increased resource allocation and having an impact on global policy frameworks. The work described in this issue by Chisholm et al. (2017, this issue) sets out to address some of the practical challenges in translating these successes into meaningful impact at a local level. The Emerald project aims to strengthen emerging health services by enhancing health system performance (Semrau et al. 2015). The development and testing of an adapted version of the World Health Organisation (WHO) OneHealth tool, described in the article, is a key contribution to supporting pragmatic decisionmaking in national and district-level service strengthening. The tool seeks to provide clear information on resources necessary to provide different packages of health care, enabling planning and balancing priorities between conditions. This version specifically focuses on services formental, neurological and substanceusedisorders (MNS) in low income settings. In addition, the tool is able to provide estimates of expected health impacts, which begins to fill an essential gap in addressing the challenge that advocates for greater equity in mental health care globally have faced in justifying investment in this historically under-resourced area. The term ‘Global Mental Health’ first gained prominence with the publication of a Lancet series on this topic (Lancet Global Mental Health, 2007), and defined a discipline that gradually articulated a common approach to application of an increasingly compelling evidence-base to improved health and equity in what had previously been a disparate and fractured body of knowledge (Patel & Prince, 2010). The initial focus of the GMH agenda has been to generate evidence for scaling up innovative services in order to narrow the treatment gap in mental health, and to address the human rights abuse experienced by people with mental conditions. This focus helped to drive an international research agenda (Collins et al. 2011), though more concrete progress has been achieved in the first of these priorities. Mental health is increasingly being recognised as an important component in global development, though the pace of implementation is lagging behind that of research. Translational research has laid an important foundation for policy and practice, producing evidencebased normative materials for treatment interventions (Barbui et al. 2010). Mental health systems have long resisted reform in low income settings, and remain chronically under-resourced (WHO, 2014). There is now strong evidence that, improved outcomes can be achieved through processes of health systems reform that decentralise services, for example through integration into secondary and primary health care, and engagement of non-specialist workers such as health and social workers through task-sharing (van Ginneken et al. 2011).