diff --git a/common/dice/dice.go b/common/dice/dice.go
index 742d563f..8e3a061a 100644
--- a/common/dice/dice.go
+++ b/common/dice/dice.go
@@ -1,3 +1,6 @@
+// Package dice contains common functions to generate random number.
+// It also initialize math/rand with the time in seconds at launch time.
+
 package dice
 
 import (
@@ -5,6 +8,7 @@ import (
 	"time"
 )
 
+// Roll returns a non-negative number between 0 (inclusive) and n (exclusive).
 func Roll(n int) int {
 	if n == 1 {
 		return 0