A COPS/PCMM developer is responsible for developing and implementing protocols for communication between network devices and service management systems in telecommunications. They use the COPS (Common Open Policy Service) protocol and PCMM (Policy Control and Charging Rules Function) framework to set rules for data transmission and ensure efficient network traffic management. They design, code, test, and debug software related to these protocols. They also maintain documentation, resolve network issues, and collaborate with network engineers to optimize network performance. Their role is crucial in managing network resources and facilitating smooth and secure communication.