---
title: "List events for an LLM Observability experiment"
method: GET
path: "/api/v2/llm-obs/v3/experiments/{experiment_id}/events"
tags: ["LLM Observability"]
---

# List events for an LLM Observability experiment

`GET /api/v2/llm-obs/v3/experiments/{experiment_id}/events`

Retrieve spans and experiment-level summary metrics for a given experiment with cursor-based pagination.

## Path parameters

- `experiment_id` string, required

## Query parameters

- `page[limit]` integer
- `page[cursor]` string

## Response `200`

OK

- LLMObsExperimentEventsV2Response — Response for listing experiment events (v2/v3). Returns spans and summary metrics in a single resource.
  - `data` LLMObsExperimentEventsV2DataResponse, required — JSON:API data object for an experiment events response.
    - `attributes` LLMObsExperimentEventsV2DataAttributesResponse, required — Attributes of an experiment events response.
      - `spans` LLMObsExperimentSpanWithEvals[], required — Experiment spans, each enriched with their associated evaluation metrics.
        - `dataset_record_id` string, nullable — ID of the dataset record this span evaluated.
        - `duration` number, double — Duration of the span in nanoseconds.
        - `eval_metrics` LLMObsExperimentEvalMetricEvent[] — Evaluation metrics associated with this span.
          - `assessment` 'pass' | 'fail' — Assessment result for an LLM Observability experiment metric.
          - `boolean_value` boolean, nullable — Boolean value. Present when `metric_type` is `boolean`.
          - `categorical_value` string, nullable — Categorical value. Present when `metric_type` is `categorical`.
          - `eval_source_type` string — Source type of the evaluation.
          - `id` string — Unique identifier of the evaluation metric event.
          - `json_value` object, nullable — JSON value. Present when `metric_type` is `json`.
          - `label` string — Label or name for the metric.
          - `metadata` object, nullable — Arbitrary metadata associated with the metric.
          - `metric_source` string — Source of the metric. Either `custom` (user-submitted) or `summary` (experiment-level aggregate).
          - `metric_type` 'score' | 'categorical' | 'boolean' | 'json' — Type of metric recorded for an LLM Observability experiment.
          - `reasoning` string, nullable — Human-readable reasoning for the metric value.
          - `score_value` number, double, nullable — Numeric score. Present when `metric_type` is `score`.
          - `span_id` string — Span ID this metric is associated with.
          - `tags` string[] — Tags associated with the metric.
          - `timestamp_ms` integer — Timestamp when the metric was recorded, in milliseconds since Unix epoch.
          - `trace_id` string — Trace ID linking this metric to a span.
        - `id` string — Unique identifier of the span.
        - `meta` LLMObsExperimentSpanMeta — Metadata associated with an experiment span.
          - `error` LLMObsExperimentSpanError — Error details for an experiment span.
            - `message` string — Error message.
            - `stack` string — Stack trace of the error.
            - `type` string — The error type or exception class name.
          - `expected_output` object — Expected output for the span, used for evaluation.
          - `input` AnyValue, nullable — An arbitrary object value with additional properties.
          - `output` AnyValue, nullable — An arbitrary object value with additional properties.
        - `metrics` object — Numeric metrics attached to the span.
        - `name` string — Name of the span.
        - `parent_id` string — Parent span ID, if any.
        - `span_id` string — Span ID.
        - `start_ns` integer — Start time in nanoseconds since Unix epoch.
        - `status` 'ok' | 'error' — Status of the span.
        - `tags` string[] — Tags associated with the span.
        - `trace_id` string — Trace ID.
      - `summary_metrics` LLMObsExperimentEvalMetricEvent[], required — Experiment-level summary evaluation metrics (not tied to individual spans).
        - `assessment` 'pass' | 'fail' — Assessment result for an LLM Observability experiment metric.
        - `boolean_value` boolean, nullable — Boolean value. Present when `metric_type` is `boolean`.
        - `categorical_value` string, nullable — Categorical value. Present when `metric_type` is `categorical`.
        - `eval_source_type` string — Source type of the evaluation.
        - `id` string — Unique identifier of the evaluation metric event.
        - `json_value` object, nullable — JSON value. Present when `metric_type` is `json`.
        - `label` string — Label or name for the metric.
        - `metadata` object, nullable — Arbitrary metadata associated with the metric.
        - `metric_source` string — Source of the metric. Either `custom` (user-submitted) or `summary` (experiment-level aggregate).
        - `metric_type` 'score' | 'categorical' | 'boolean' | 'json' — Type of metric recorded for an LLM Observability experiment.
        - `reasoning` string, nullable — Human-readable reasoning for the metric value.
        - `score_value` number, double, nullable — Numeric score. Present when `metric_type` is `score`.
        - `span_id` string — Span ID this metric is associated with.
        - `tags` string[] — Tags associated with the metric.
        - `timestamp_ms` integer — Timestamp when the metric was recorded, in milliseconds since Unix epoch.
        - `trace_id` string — Trace ID linking this metric to a span.
    - `id` string, required — Identifier for this events resource.
    - `type` 'experiment_events', required — Resource type for an experiment events collection.
  - `meta` LLMObsCursorMeta — Pagination cursor metadata.
    - `after` string, nullable — Cursor for the next page of results.

## Other responses

- `400` — Bad Request
- `401` — Unauthorized
- `403` — Forbidden
- `404` — Not Found
- `429` — Too many requests
- `500` — Internal Server Error

---

[API](https://skmtc.dev/datadog/apis/api-v2.md) · [All operations](https://skmtc.dev/datadog/apis/api-v2/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/datadog/api-v2/revisions/da68bf029e4c/schema)