Agent tracing is useful because it reveals execution structure: which step ran, which tool failed, where a retry occurred, how long a model call took, and how the token budget changed. The easiest implementation is to capture every prompt, argument, result, and response. It is also the easiest way to turn an observability system into a second copy of sensitive application data. Metadata-only tracing takes a different approach. It records the behavior of an agent without storing its raw p...