The correct command is oci monitoring metric-data summarize-metrics-data. Oracle defines this operation specifically for retrieving aggregated metric data that matches a Monitoring Query Language (MQL) expression. The command accepts parameters including the compartment OCID, metric namespace, and --query-text, which can contain expressions such as CpuUtilization[1m].mean(). The post operation performs the opposite function: it publishes custom metric data into OCI Monitoring rather than retrieving it. query and retrieve are not valid subcommands under oci monitoring metric-data. Therefore, when an automation script must obtain aggregated CPU utilization or another metric series from Monitoring, summarize-metrics-data is the documented OCI CLI operation.