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Cartesia scores completed calls with built-in metrics and custom metrics assigned to the agent. Use built-in metrics for runtime health and custom metrics for outcomes specific to your application. Through the API, you can create custom metrics, add them to or remove them from an agent, and list or export results. You can also do this via the Playground UI as shown below.

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Built-in metrics

Cartesia calculates these metrics for every call:

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Custom metrics

Create an LLM-as-a-judge metric in the Playground, or with POST /agents/metrics, using a name and evaluation prompt. The prompt should define one concrete question and the expected output. Test it against representative call transcripts before assigning it to an agent.
Metric names must be unique within your organization. They may contain lowercase letters, numbers, hyphens, underscores, and periods.

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Assign a metric

Assign metrics from the agent page in the Playground, or with POST /agents/{agent_id}/metrics/{metric_id}. Cartesia evaluates subsequent calls for that agent; assigning a metric does not evaluate earlier calls.
Assign a metric to an agent
See Results to retrieve and export metric results.