diff --git a/types.d.ts b/types.d.ts
index 67ee3a5f..d6fcaf0f 100644
--- a/types.d.ts
+++ b/types.d.ts
@@ -1,2 +1,12 @@
 export function isValid(email: string): boolean
 export function blacklist(): Set<string>
+/**
+ * Adds custom domains to the Mailchecker module.
+ *
+ * This function enhances the default email validation behavior by allowing you to extend
+ * the recognized list of email domains. The provided custom domains will be checked alongside
+ * the built-in domains.
+ *
+ * @param domains - An array of custom domain strings to be added.
+ */
+export function addCustomDomains(domains: string[]): void