diff --git a/app/gateway/sandboxing.md b/app/gateway/sandboxing.md
index 877d72f0654..bbc4ff6d854 100644
--- a/app/gateway/sandboxing.md
+++ b/app/gateway/sandboxing.md
@@ -304,6 +304,15 @@ kong.tracing.set_should_sample
 kong.tracing.start_span
 ```
 
+#### Kong Metrics PDK
+
+```
+kong.metrics.counter
+kong.metrics.gauge
+kong.metrics.histogram
+kong.metrics.VALUE_TYPE
+```
+
 #### Nginx Constants
 ```
 ngx.AGAIN                     ngx.ALERT