The Prometheus Rule Evaluator validates alerting and recording rules before deployment to production Prometheus instances. It parses rule YAML files following the Prometheus rule_group schema and tests each rule expression against historical metrics data via the Prometheus HTTP API /api/v1/query_range endpoint. For each rule, the evaluator runs the PromQL expression across configurable time windows (default: 7 days) to determine historical firing patterns. The skill reports false positive rates, alert frequency, and duration distributions to help tune thresholds before deployment. It supports all PromQL functions including rate(), histogram_quantile(), predict_linear(), and aggregation operators. Test scenarios can be defined in YAML format specifying expected alert states at given timestamps, enabling unit-test-style validation of alerting logic. The evaluator integrates with the Prometheus /api/v1/rules endpoint to compare proposed rules against existing active rules, detecting conflicts and redundancies. Output includes a coverage report showing which metrics are monitored, gaps in monitoring, and recommendations for additional rules based on available metric labels. Compatible with Thanos and Cortex long-term storage backends via their compatible query APIs.