---
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`

## Request

- Base URL: `https://api.datadoghq.com`
- URL: `https://api.datadoghq.com/api/v2/llm-obs/v3/experiments/{experiment_id}/events`
- Auth: API key in header `DD-API-KEY` and API key in header `DD-APPLICATION-KEY`

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/datadog-api-v2-collection.md) - [All operations](https://skmtc.dev/datadog/apis/datadog-api-v2-collection/llms.txt) - [OpenAPI document](https://skmtc.dev/datadog/apis/datadog-api-v2-collection/revisions/da68bf029e4c?raw)