diff --git a/cylc/flow/xtriggers/xrandom.py b/cylc/flow/xtriggers/xrandom.py
index 218470e4d12..d883645276f 100644
--- a/cylc/flow/xtriggers/xrandom.py
+++ b/cylc/flow/xtriggers/xrandom.py
@@ -100,9 +100,12 @@ def xrandom(
 
 
 def validate(args: Dict[str, Any]):
-    """Validate and manipulate args parsed from the workflow config.
+    """Validate the args that xrandom is called with.
+
+    Cylc calls this function automatically when parsing the workflow.
+
+    Here we specify the rules for args are:
 
-    The rules for args are:
     * percent: Must be 0 ≤ x ≤ 100
     * secs: Must be an integer.
     """