diff --git a/Sources/AmiiboService/openapi.yaml b/Sources/AmiiboService/openapi.yaml
index 45986d3..8cf7d16 100644
--- a/Sources/AmiiboService/openapi.yaml
+++ b/Sources/AmiiboService/openapi.yaml
@@ -357,6 +357,8 @@ components:
 
             The positions 0 to 7 of the hexadecimal string.
           type: string
+          pattern: "^[0-9a-fA-F]+$"
+          minLength: 8
           maxLength: 8
         image:
           description: An image URL related to an amiibo.
@@ -374,6 +376,8 @@ components:
 
             The positions 8 to 15 of the hexadecimal string.
           type: string
+          pattern: "^[0-9a-fA-F]+$"
+          minLength: 8
           maxLength: 8
         type:
           description: A name for the type an amiibo belongs to.