The focus of this case study is the study design and the process of developing a specific type of study tool—clinical vignettes. It is based on my master’s dissertation, where I, in collaboration with a research team, measured the level of competence among peripheral female health care workers known as auxiliary nurses and midwives (ANMs), constituting 30% of the health care work force in India. The unavailability of published data on the accuracy of detection and management of common conditions in Indian communities where ANMs are the first-line health care provider intrigued us to conduct this study. The objectives were to assess the competency of the peripheral health workers in detection and management of common illnesses they encounter in their practice and the factors associated with inadequate competency. We choose cross-sectional design to answer them. By referring to a study done in a similar setting, we calculated the sample size and used simple random sampling technique for selecting participants. In the absence of standard clinical vignettes for measuring competence, we developed condition-specific clinical vignettes following extensive literature review. The clinical vignettes underwent both content and face validation processes. We allotted equal time to the participants to fill the clinical vignettes and assigned scores to the answers according to predecided plan constructed from literature review. We also collected information on other possible factors which could be related to inadequate competency using a pretested questionnaire and finally used multiple logistic regression to identify the factors associated with inadequate competency.