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The Tool calls page shows how your agents use functions across all their calls. Open Observability → Tool calls to see which tools run most often, which ones fail, and the calls behind each result.

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Overview

The summary reports:
  • Total tool invocations in the selected period.
  • Number of unique tools invoked.
  • Success rate across invocations with a known success or error outcome.
  • Failed invocations.
The activity chart plots daily tool-call volume and failures. Use the agent, status, time-window, and tool-name filters to narrow both the summary and the table. Filters stay in the URL, so a filtered view can be shared.

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Tool health table

Each row represents one observed tool and includes its invocation count, number of calls affected, success rate, failures, P90 duration, and most recent invocation. Select a row to inspect its latest invocations without leaving the list. The invocation panel shows the agent, provider, outcome, arguments, result, error message, and a link to the original conversation. Arguments and results are collapsed by default so large payloads do not crowd the timeline.
P90 duration is available only when the agent exports timed OpenTelemetry tool spans. Provider history without duration data shows no duration instead of a misleading zero.

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Outcome handling

Zelto classifies a tool invocation as: Unknown outcomes are counted in total usage but excluded from the success-rate denominator. This prevents missing provider metadata from being treated as a successful execution.
  • Conversations: each invocation appears inline with the transcript.
  • Traces: tool spans appear in the full OpenTelemetry waterfall.
  • Tool-check monitors: continuously verify that an expected tool executed correctly on each call.