This paper explores the design and deployment of classroom observation tools to support teacher professional development and instructional supervision in low-resource and crisis-affected settings. Drawing on a rapid evidence scan conducted for the Ministry of Education in Yemen, the study reviews international classroom observation frameworks and assesses two observation tools currently used to support general pedagogy and early grade literacy instruction. The review identifies five key principles of effective observation systems: technical quality, pedagogical relevance, standardisation, clarity of purpose, and contextual alignment. Findings suggest that while the Yemeni tools align well with recognised dimensions of effective teaching and literacy instruction, they face challenges related to reliability, scoring consistency, and the provision of actionable feedback for teacher improvement. The paper argues that classroom observation tools are most effective when used as developmental instruments that support coaching and professional growth. It concludes with practical recommendations for strengthening tool design, observer training, and implementation approaches in resource-constrained education systems. An output of the EdTech Hub, https://edtechhub.org/