Observability has become crucial in multicloud environments, and OpenTelemetry is a leading open-source tool for collecting observability telemetry data. The series explores how OpenTelemetry provides insights into application performance and runtime details through its SDKs and libraries, which allow instrumentation across various platforms and languages. The final part of the series introduces Dynatrace's OneAgent as a tool that enhances telemetry data collection with minimal effort, by automatically monitoring supported technologies and offering additional insights into host performance, application and service monitoring, real user monitoring, and database performance. OneAgent seamlessly integrates with OpenTelemetry, extending its capabilities by providing a comprehensive view of the system and services, including detailed metrics such as CPU usage, DNS query times, and database call durations. This integration results in full observability, facilitating better understanding and debugging of applications and systems by capturing a broad range of metrics that vanilla OpenTelemetry instrumentation might miss.