The anatomy of a trace

A trace is a tree of spans. The root is your agent run. Every model call, tool call and guardrail check is a child with a start, an end and a bag of attributes.

Read the shape first

Before reading any text, look at the waterfall. A long bar with nothing under it is a model thinking. A staircase is sequential tool calls that could run in parallel.

Then the three numbers

• Latency of the root span

• Tokens in and out

• Cost of the run

Then the words

Only now open the prompt and the response. By this point you usually know which span to open.