Context: In the light of the swift and iterative nature of Agile Software Development (ASD) practices, establishing deeper insights into capability measurement within the context of team formation is crucial, as the capability of individuals and teams can affect team performance and productivity. Although a former Systematic Literature Review (SLR) synthesized the state of the art in relation to capability measurement in ASD with a focus on selecting individuals to agile teams, and capabilities related to team performance and success, determining to what degree the SLR's results apply to practice can provide progressive insights to both research and practice. Objective: Our study investigates how agile practitioners perceive the relevance of individual and team level measures for characterizing the capability of an agile team and its members. Furthermore, to scrutinize variations in practitioners' perceptions, our study further analyzes perceptions across stratified demographic groups. Method: We undertook a Web-based survey using a questionnaire built based on the capability measures identified from a previously conducted SLR. Results: Our survey responses (60) indicate that 127 individual and 28 team capability measures were considered as relevant by the majority of practitioners. We also identified seven individual and one team capability measure that have not been previously characterized by our SLR. The surveyed practitioners suggested that an agile team member's responsibility and questioning skills significantly represent the member's capability. Conclusion: Results from our survey align with our SLR's findings. Measures associated with social aspects were observed to be dominant compared to technical and innovative aspects. Our results can support agile practitioners in their team composition decisions.