Introduction: The integration of an informative and inclusive monitoring, evaluation and learning process which requires appropriate tools and methods is crucial to the effective implementation of early childhood interventions. Most of the child development assessment tools that have been constructed for use in sub-Saharan Africa consider the need to be affordable and feasibly administered by those with limited previous experience. These tools include the Kilifi Developmental Inventory (KDI), the A-not-B task, the Developmental Milestones Checklist, and the Profile for Socio-Emotional Development (PSED) which each use different approaches such as direct child assessment, observation, and parental reports. Whereas these tools have demonstrated good psychometric properties, each of them focusses either on only one or two child developmental domains, does not adequately measure all aspects of the different domains that are theoretically affected by a risk factor or intervention, or is not in sufficient depth. We therefore constructed a tool that combined these separate measures into one assessment schedule – the Protocol for Child Monitoring – Infant/Toddler version (PCM-IT). We subjected the combined tool to a process of pilot testing and validation to establish its psychometric properties, the feasibility of administration and acceptability.Method: The framework of five aspirations (inclusive, informative, people-centered, dynamic and interactive) that guide effective intervention delivery mechanisms was used to structure the evaluation of the PCM-IT. The piloting of the administration of the PCM-IT was based on a proof-of-concept study with a multi-arm pre-post design in Kibera and Kangemi, while the validation study was carried out in Mathare. The three areas are informal settlements in Nairobi. The results of the pilot study informed the selection of items that were included in the validation study.Results: The timed items were too difficult for the children included in the study and were therefore excluded. Overall, the PCM-IT had excellent reliability levels. Children’s raw sub-scale and overall developmental scores were normally distributed. There were weak to moderate correlations across the different domains. Speed and fluency of administration of items among the assessment team improved with practice and familiarity. The tool was perceived as providing holistic information about a child’s performance. Conclusion: The aspirations of Measurement for Change including the need for a tool development and administration process to be inclusive, informative, people-centered, and dynamic were met to a large extent. The aspiration of being interactive would be better met through an exploration of the use of the tool to engage with families to strengthen the quality of their nurturing care practices.