How it works
Observability tools intercept LLM calls and tool calls, log them with structured metadata (inputs, outputs, latency, cost, errors), store them for later querying, and alert on anomalies. Production agents log every prompt, every model response, every tool call with inputs and outputs.
Example
When a customer service agent goes wrong (resolves a ticket incorrectly), the on-call engineer pulls the trace in Langfuse: sees the system prompt, the customer message, the tool calls in order, the tool outputs, and the final response — debugs in 5 minutes instead of 5 hours.