Indonesia has changed the national assessment of school students from the national exam (NE) to the minimum competency assessment (MCA) in 2021. In the minimum competency assessment, one of the student's abilities measured is numeracy skills. So that the valid, practical, and effective assessment instruments that evaluate students' numeracy skills are needed. This study described the feasibility of developing a numeracy test instrument for minimum competency assessments and described students' numeracy abilities. This research was development research. This research involved junior high school students with different mathematical abilities. The data were analyzed descriptively by collecting observations, tests and document analysis. This study showed that the development of test instruments could be used as a reference to measure students' numeracy skills. The test instrument was categorized as very feasible, valid and practical. The test results indicated that there was a potential effect on students' numeracy skills. In solving numeracy test questions, the potential effect of the test instrument on numeracy skills was 75.69%, with the emerging mathematical understanding ability of 80.22%, the ability to apply mathematics in problem-solving by 74.94%, and mathematical reasoning ability of 71.93%.