diff --git a/README.md b/README.md
index 488c5c0..c1f4c8a 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,7 @@ Extension methods and classes I often find useful for C# development.
 
 Attribute classes to validate properties in models.
 
+- **`AlphaOnlyAttribute`**: Check that a string only contains letters.
 - **`UniqueItemsAttribute`**: Check that a collection property does not contain duplicate items.
 
 ## Collections