diff --git a/mon-system/prometheus-rules.yaml b/mon-system/prometheus-rules.yaml
index 7ee294b..e1cfb02 100644
--- a/mon-system/prometheus-rules.yaml
+++ b/mon-system/prometheus-rules.yaml
@@ -216,6 +216,8 @@ data:
   # "normal conditions" figures: 700 Mbit/s down / 28 Mbit/s up.
   # Throughput is sampled every ~15 min, so `for:` spans >=2 samples to avoid
   # firing on a single fluke. Recalibrate floors after a week of baseline data.
+  # NOTE: uses Prometheus template funcs (humanize/humanizePercentage/humanizeDuration);
+  # mul/div are NOT valid Prometheus template functions.
   wan-alerts.yml: |
     groups:
       - name: wan-quality-alerts
@@ -228,7 +230,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN upstream packet loss to {{ $labels.target }}"
-              description: "irtt upstream loss {{ printf \"%.2f\" (mul $value 100) }}% (>1%) for 2m. Cable-upstream symptom; capture for ISP."
+              description: "irtt upstream loss {{ $value | humanizePercentage }} (>1%) for 2m. Cable-upstream symptom; capture for ISP."
 
           - alert: WanDownstreamPacketLoss
             expr: wan_irtt_loss_ratio{direction="downstream",condition="idle"} > 0.01
@@ -237,7 +239,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN downstream packet loss to {{ $labels.target }}"
-              description: "irtt downstream loss {{ printf \"%.2f\" (mul $value 100) }}% (>1%) for 2m."
+              description: "irtt downstream loss {{ $value | humanizePercentage }} (>1%) for 2m."
 
           # --- latency / jitter ---
           - alert: WanLatencyHigh
@@ -247,7 +249,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN RTT spikes to {{ $labels.target }}"
-              description: "irtt max RTT > 80 ms for 5m (idle). Real-time apps will feel this."
+              description: "irtt max RTT {{ $value | humanizeDuration }} (>80 ms) for 5m (idle). Real-time apps will feel this."
 
           - alert: WanJitterHigh
             expr: wan_irtt_jitter_seconds{direction="round_trip",condition="idle"} > 0.03
@@ -256,7 +258,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN jitter high to {{ $labels.target }}"
-              description: "Round-trip jitter > 30 ms for 5m. Degrades VoIP/video."
+              description: "Round-trip jitter {{ $value | humanizeDuration }} (>30 ms) for 5m. Degrades VoIP/video."
 
           # --- bufferbloat: latency added while the line is saturated ---
           - alert: WanBufferbloat
@@ -270,7 +272,7 @@ data:
               severity: info
             annotations:
               summary: "WAN bufferbloat on {{ $labels.target }}"
-              description: "RTT rises {{ printf \"%.0f\" (mul $value 1000) }} ms under load (>100 ms). Line buckles when saturated."
+              description: "RTT rises {{ $value | humanizeDuration }} under load (>100 ms). Line buckles when saturated."
 
           # --- throughput vs One.hu "normal" 700/28 (alert below 50%) ---
           - alert: WanDownloadDegraded
@@ -280,7 +282,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN download below half of plan"
-              description: "Download {{ printf \"%.0f\" (div $value 1e6) }} Mbit/s (< 350, half of 700 normal) for 20m."
+              description: "Download {{ $value | humanize }}bit/s (< 350M, half of 700 normal) for 20m."
 
           - alert: WanUploadDegraded
             expr: wan_throughput_bits_per_second{direction="upload"} < 14e6
@@ -289,7 +291,7 @@ data:
               severity: warning
             annotations:
               summary: "WAN upload below half of plan"
-              description: "Upload {{ printf \"%.1f\" (div $value 1e6) }} Mbit/s (< 14, half of 28 normal) for 20m."
+              description: "Upload {{ $value | humanize }}bit/s (< 14M, half of 28 normal) for 20m."
 
           # --- the monitor itself stopped producing data ---
           - alert: WanProbeStalled