Loki metric queries return null labels for aggregate groupings

[IS-PatrickSmith]

Problem

When executing Loki metric queries with aggregate functions like sum by() using the query_loki_logs tool, the results include metric values but all label groupings return as null.

Expected Behavior

Metric queries with grouping should return the labels that were grouped by. For example:

sum by(app, namespace) (count_over_time({namespace="dev2"} | json | Level="Error" [3h])) > 0

Should return results with app and namespace labels populated.

Actual Behavior

The query executes successfully but all results have "labels": null:

[
  {"timestamp":"1761755580","line":"5","labels":null},
  {"timestamp":"1761755623","line":"5","labels":null},
  ...
]

Steps to Reproduce

1. Configure Grafana MCP with a Loki datasource
2. Execute a metric query with grouping:

query_loki_logs(
  datasourceUid="<loki-uid>",
  logql='sum by(app, namespace) (count_over_time({namespace="dev2"} [3h])) > 0',
  ...
)

3. Observe that labels field is null in all results

Workaround

Instead of using metric queries, fetch raw log samples and extract labels from individual log entries.

Environment

• Grafana MCP version: latest (Docker image mcp/grafana)
• Transport: stdio via Docker