The Nurse Assistant App (NAA) was developed to improve the quality of antenatal care in Magu District Tanzania by providing digital assistance to healthcare workers. The NAA guides healthcare workers step by step through all necessary antenatal care interventions and provides tailored advice and suggestions for follow-up actions. We used the Intervention Mapping framework to retrospectively evaluate the development of the NAA. Methods Desk research into the content, evidence base, and development of the NAA was performed combined with semi-structured interviews with two initial developers to fill in a planning tool consisting of 40 criteria for systematic evaluation of the data. Results Findings showed that the NAA was developed based on existing literature on antenatal care guidelines as well as the knowledge and experience of a broad variety of stakeholders and that five of the six steps of Intervention Mapping were performed. However, the development of the NAA lacked a theoretical foundation on behaviour change models. Future research will focus on the experiences of healthcare workers providing antenatal care using the NAA. Conclusions The NAA was developed in collaboration with relevant stakeholders and took practical matters as well as evidence from existing literature into account. However, we recommend that the responsibility and ownership of the NAA should be shared with the local government to increase the potential and sustainability of the NAA. Key messages The NAA was developed to improve the quality of antenatal care in rural Tanzania targeting healthcare workers. The current evaluation informs future digital health tool developers in sub-Saharan Africa about elements to take into account during the development phase such as systematic mapping of the process.