diff --git a/helm/agents/observability/templates/agent.yaml b/helm/agents/observability/templates/agent.yaml
index 6132ae2d7..752df2d03 100644
--- a/helm/agents/observability/templates/agent.yaml
+++ b/helm/agents/observability/templates/agent.yaml
@@ -22,6 +22,12 @@ spec:
       - **Kubernetes Observability**: You comprehend service monitoring, resource utilization patterns, and common performance bottlenecks.
       - **Metrics Interpretation**: You can analyze trends, anomalies, and correlations in observability data.
       - **Alerting Design**: You can recommend effective alerting strategies based on metrics and thresholds.
+      {{- with .Values.grafana.prometheusDatasourceName }}
+
+      ## Prometheus Datasource
+
+      Before making any Prometheus tool call, you must first call get_datasource with name "{{ . }}" to resolve the datasource UID. Use that UID for all subsequent Prometheus tool calls (query_prometheus, list_prometheus_metric_names, list_prometheus_label_names, list_prometheus_label_values, list_prometheus_metric_metadata).
+      {{- end }}
 
       {{ `{{include "builtin/kubernetes-context"}}` }}
 
@@ -94,8 +100,7 @@ spec:
           - get_sift_analysis
           - get_oncall_shift
           - get_incident
-          - get_datasource_by_uid
-          - get_datasource_by_name
+          - get_datasource
           - get_dashboard_panel_queries
           - get_dashboard_by_uid
           - get_current_oncall_users
diff --git a/helm/agents/observability/values.yaml b/helm/agents/observability/values.yaml
index 7de147c56..ad21da5c7 100644
--- a/helm/agents/observability/values.yaml
+++ b/helm/agents/observability/values.yaml
@@ -19,3 +19,8 @@ compaction: {}
 podSecurityContext: {}
 
 securityContext: {}
+
+# -- Optional Grafana datasource name for Prometheus (e.g. "Prometheus"). When set, the agent
+# uses this datasource name for all Prometheus queries instead of discovering it at runtime.
+grafana:
+  prometheusDatasourceName: ""