diff --git a/API.md b/API.md
index dce009d..e9af9ba 100644
--- a/API.md
+++ b/API.md
@@ -1,6 +1,63 @@
 # API Reference <a name="API Reference" id="api-reference"></a>
 
 
+## Structs <a name="Structs" id="Structs"></a>
+
+### ResourceAutoNaming <a name="ResourceAutoNaming" id="@gammarers/aws-resource-naming.ResourceAutoNaming"></a>
+
+#### Initializer <a name="Initializer" id="@gammarers/aws-resource-naming.ResourceAutoNaming.Initializer"></a>
+
+```typescript
+import { ResourceAutoNaming } from '@gammarers/aws-resource-naming'
+
+const resourceAutoNaming: ResourceAutoNaming = { ... }
+```
+
+#### Properties <a name="Properties" id="Properties"></a>
+
+| **Name** | **Type** | **Description** |
+| --- | --- | --- |
+| <code><a href="#@gammarers/aws-resource-naming.ResourceAutoNaming.property.type">type</a></code> | <code><a href="#@gammarers/aws-resource-naming.ResourceNamingType">ResourceNamingType</a></code> | *No description.* |
+
+---
+
+##### `type`<sup>Required</sup> <a name="type" id="@gammarers/aws-resource-naming.ResourceAutoNaming.property.type"></a>
+
+```typescript
+public readonly type: ResourceNamingType;
+```
+
+- *Type:* <a href="#@gammarers/aws-resource-naming.ResourceNamingType">ResourceNamingType</a>
+
+---
+
+### ResourceDefaultNaming <a name="ResourceDefaultNaming" id="@gammarers/aws-resource-naming.ResourceDefaultNaming"></a>
+
+#### Initializer <a name="Initializer" id="@gammarers/aws-resource-naming.ResourceDefaultNaming.Initializer"></a>
+
+```typescript
+import { ResourceDefaultNaming } from '@gammarers/aws-resource-naming'
+
+const resourceDefaultNaming: ResourceDefaultNaming = { ... }
+```
+
+#### Properties <a name="Properties" id="Properties"></a>
+
+| **Name** | **Type** | **Description** |
+| --- | --- | --- |
+| <code><a href="#@gammarers/aws-resource-naming.ResourceDefaultNaming.property.type">type</a></code> | <code><a href="#@gammarers/aws-resource-naming.ResourceNamingType">ResourceNamingType</a></code> | *No description.* |
+
+---
+
+##### `type`<sup>Required</sup> <a name="type" id="@gammarers/aws-resource-naming.ResourceDefaultNaming.property.type"></a>
+
+```typescript
+public readonly type: ResourceNamingType;
+```
+
+- *Type:* <a href="#@gammarers/aws-resource-naming.ResourceNamingType">ResourceNamingType</a>
+
+---
 
 
 
diff --git a/src/index.ts b/src/index.ts
index 2a6a6e9..327e499 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -14,11 +14,11 @@ export enum ResourceNamingType {
   CUSTOM = 'Custom',
 }
 
-export type ResourceAutoNaming = {
+export interface ResourceAutoNaming {
   readonly type: ResourceNamingType.AUTO;
 }
 
-export type ResourceDefaultNaming = {
+export interface ResourceDefaultNaming {
   readonly type: ResourceNamingType.DEFAULT;
 }
 
@@ -64,6 +64,7 @@ export namespace ResourceNaming {
   //  function getValueByKey<K extends keyof MyObject>(obj: MyObject, key: K): MyObject[K] {
   //    return obj[key];
   //  }
+  type ResourceNamingOption = ResourceAutoNaming | ResourceDefaultNaming | {type: ResourceNamingType.CUSTOM; [key: string]: string};
 
   //  export type NamingOptions = {
   //    naming: ResourceNaming.AutoNaming | ResourceNaming.DefaultNaming | {type: ResourceNaming.NamingType.CUSTOM; names: {[key: string]: string}};
@@ -79,7 +80,7 @@ export namespace ResourceNaming {
     //    resourceNaming?: {
     //      naming: ResourceNaming.AutoNaming | ResourceNaming.DefaultNaming | {type: ResourceNaming.NamingType.CUSTOM; names: {[key: string]: string}};
     //    }) {
-    resourceNaming?: ResourceAutoNaming | ResourceDefaultNaming | {type: ResourceNamingType.CUSTOM; [key: string]: string}) {
+    resourceNaming?: ResourceNamingOption) {
     return Object.fromEntries(
       Object.entries(autoNaming).map(([name, value]) => {
         return [name, (() => {
diff --git a/test/naming.test.ts b/test/naming.test.ts
index 90e73e7..6eca1bb 100644
--- a/test/naming.test.ts
+++ b/test/naming.test.ts
@@ -18,7 +18,7 @@ describe('ResouceNaming Testing', () => {
     functionRoleName: `${random}-func-exc-role`,
   };
 
-  type CustomNaming = {
+  interface CustomNaming {
     readonly type: ResourceNamingType.CUSTOM;
     readonly functionName: 'example-function';
     readonly functionRoleName: 'example-role';
@@ -52,7 +52,7 @@ describe('ResouceNaming Testing', () => {
   });
 
   it('Is Namings', () => {
-    const options: ResourceNamingOption = {
+    const options = {
       type: ResourceNamingType.CUSTOM,
       functionName: 'example-function',
       functionRoleName: 'example-role',