Tracing

Tracing records a multi-step operation — a chain, a RAG pipeline, an agent run — as a tree of spans, each with inputs, outputs, timing and token usage.

It is the right tool for debugging agent behaviour, where the interesting question is which step went wrong and what it was given.

It requires instrumentation, which means it sees only what you instrumented. Traffic from scripts, notebooks and forgotten services is invisible — which is often exactly the traffic that surprises you on a bill.