metrics: expose --fn aggregation on service metrics series

internal/tiger/cmd/service.go

@@ -1822,6 +1822,7 @@ func buildServiceMetricsSeriesCmd() *cobra.Command {
 	var role string
 	var filters []string
 	var bucketSeconds int
+	var fn string
 	var output string
 
 	cmd := &cobra.Command{
@@ -1890,6 +1891,10 @@ Examples:
 				bs := bucketSeconds
 				body.BucketSeconds = &bs
 			}
+			if fn != "" {
+				f := api.MetricsSeriesRequestFn(strings.ToUpper(fn))
+				body.Fn = &f
+			}
 			if len(labelFilters) > 0 {
 				body.Filters = &labelFilters
 			}
@@ -1920,6 +1925,7 @@ Examples:
 	cmd.Flags().StringVar(&role, "role", "", "Filter to a specific instance role (PRIMARY or REPLICA)")
 	cmd.Flags().StringSliceVar(&filters, "filter", nil, "Arbitrary label filter as name=value (repeatable)")
 	cmd.Flags().IntVar(&bucketSeconds, "bucket-seconds", 0, "Aggregation bucket size in seconds (optional; server auto-selects based on the time window when omitted, minimum 60s)")
+	cmd.Flags().StringVar(&fn, "fn", "", "Aggregation function applied per bucket. One of: RATE, INCREASE, SUM, AVG, MIN, MAX, COUNT, P50, P90, P99, LAST. Rejected on the timescale_cloud_* resource/qps/connections/jobs metrics; omit to let the server pick the default")
 	cmd.Flags().VarP((*outputFlag)(&output), "output", "o", "Output format (json, yaml, table)")
 
 	cmd.MarkFlagRequired("metric")

internal/tiger/mcp/service_tools.go

@@ -455,6 +455,7 @@ type ServiceMetricsSeriesInput struct {
 	Role          string                   `json:"role,omitempty"`
 	Filters       []MetricLabelFilterInput `json:"filters,omitempty"`
 	BucketSeconds int                      `json:"bucket_seconds,omitempty"`
+	Fn            string                   `json:"fn,omitempty"`
 }
 
 func (ServiceMetricsSeriesInput) Schema() *jsonschema.Schema {
@@ -484,6 +485,10 @@ func (ServiceMetricsSeriesInput) Schema() *jsonschema.Schema {
 	schema.Properties["bucket_seconds"].Minimum = util.Ptr(60.0)
 	schema.Properties["bucket_seconds"].Examples = []any{60, 300, 3600}
 
+	schema.Properties["fn"].Description = "Aggregation function applied per bucket. Not accepted on these metrics (returns INVALID_REQUEST): timescale_cloud_system_cpu_total_millicores, timescale_cloud_system_cpu_usage_millicores, timescale_cloud_system_disk_io_read_bytes, timescale_cloud_system_disk_io_read_ops, timescale_cloud_system_disk_io_total_bytes, timescale_cloud_system_disk_io_total_ops, timescale_cloud_system_disk_io_write_bytes, timescale_cloud_system_disk_io_write_ops, timescale_cloud_system_disk_usage_bytes, timescale_cloud_system_memory_total_bytes, timescale_cloud_system_memory_usage_bytes, timescale_cloud_database_qps, timescale_cloud_database_num_connections, timescale_cloud_database_job_duration_usecs, timescale_cloud_database_job_success. When omitted, the server picks a sensible default for the metric (typically LAST)."
+	schema.Properties["fn"].Enum = []any{"RATE", "INCREASE", "SUM", "AVG", "MIN", "MAX", "COUNT", "P50", "P90", "P99", "LAST"}
+	schema.Properties["fn"].Examples = []any{"RATE"}
+
 	return schema
 }
 
@@ -1420,6 +1425,10 @@ func (s *Server) handleServiceMetricsSeries(ctx context.Context, req *mcp.CallTo
 		bs := input.BucketSeconds
 		body.BucketSeconds = &bs
 	}
+	if input.Fn != "" {
+		fn := api.MetricsSeriesRequestFn(strings.ToUpper(input.Fn))
+		body.Fn = &fn
+	}
 	if len(filters) > 0 {
 		body.Filters = &filters
 	}

openapi.yaml

@@ -1555,6 +1555,42 @@ components:
             Must be coarse enough for the window's tier; requests that ask
             for a finer bucket than the tier can produce are rejected.
           example: 3600
+        fn:
+          type: string
+          enum:
+            - RATE
+            - INCREASE
+            - SUM
+            - AVG
+            - MIN
+            - MAX
+            - COUNT
+            - P50
+            - P90
+            - P99
+            - LAST
+          description: |
+            Aggregation function applied per bucket. Optional: when omitted,
+            the server picks the default for the metric (currently `LAST`).
+
+            Not accepted on the following metrics — requests are rejected
+            with `INVALID_REQUEST`:
+              - `timescale_cloud_system_cpu_total_millicores`
+              - `timescale_cloud_system_cpu_usage_millicores`
+              - `timescale_cloud_system_disk_io_read_bytes`
+              - `timescale_cloud_system_disk_io_read_ops`
+              - `timescale_cloud_system_disk_io_total_bytes`
+              - `timescale_cloud_system_disk_io_total_ops`
+              - `timescale_cloud_system_disk_io_write_bytes`
+              - `timescale_cloud_system_disk_io_write_ops`
+              - `timescale_cloud_system_disk_usage_bytes`
+              - `timescale_cloud_system_memory_total_bytes`
+              - `timescale_cloud_system_memory_usage_bytes`
+              - `timescale_cloud_database_qps`
+              - `timescale_cloud_database_num_connections`
+              - `timescale_cloud_database_job_duration_usecs`
+              - `timescale_cloud_database_job_success`
+          example: "RATE"
         filters:
           type: array
           description: |