diff --git a/maths/factorial.py b/maths/factorial.py
index ba61447c7564..93356ea8b151 100644
--- a/maths/factorial.py
+++ b/maths/factorial.py
@@ -2,6 +2,15 @@
 Factorial of a positive integer -- https://en.wikipedia.org/wiki/Factorial
 """
 
+"""
+Implementation of factorial algorithms (iterative and recursive).
+
+Provides:
+- Strict input validation
+- Doctest examples
+- Type hints
+"""
+
 
 def factorial(number: int) -> int:
     """