diff --git a/packages/backend/src/server/api/endpoints/email-address/available.ts b/packages/backend/src/server/api/endpoints/email-address/available.ts
index 0f13b14d01..786a16a29f 100644
--- a/packages/backend/src/server/api/endpoints/email-address/available.ts
+++ b/packages/backend/src/server/api/endpoints/email-address/available.ts
@@ -2,42 +2,14 @@ import { Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { EmailService } from '@/core/EmailService.js';
 
-export const meta = {
-	tags: ['users'],
-
-	requireCredential: false,
-
-	res: {
-		type: 'object',
-		optional: false, nullable: false,
-		properties: {
-			available: {
-				type: 'boolean',
-				optional: false, nullable: false,
-			},
-			reason: {
-				type: 'string',
-				optional: false, nullable: true,
-			},
-		},
-	},
-} as const;
-
-export const paramDef = {
-	type: 'object',
-	properties: {
-		emailAddress: { type: 'string' },
-	},
-	required: ['emailAddress'],
-} as const;
-
 // eslint-disable-next-line import/no-default-export
 @Injectable()
-export default class extends Endpoint<typeof meta, typeof paramDef> {
+export default class extends Endpoint<'email-address/available'> {
+	name = 'email-address/available' as const;
 	constructor(
 		private emailService: EmailService,
 	) {
-		super(meta, paramDef, async (ps, me) => {
+		super(async (ps, me) => {
 			return await this.emailService.validateEmailForAccount(ps.emailAddress);
 		});
 	}
diff --git a/packages/misskey-js/src/endpoints.ts b/packages/misskey-js/src/endpoints.ts
index f6fe40fa73..236ff8bb09 100644
--- a/packages/misskey-js/src/endpoints.ts
+++ b/packages/misskey-js/src/endpoints.ts
@@ -4171,6 +4171,38 @@ export const endpoints = {
 		}],
 	},
 	//#endregion
+
+	'email-address/available': {
+		tags: ['users'],
+	
+		requireCredential: false,
+	
+		defines: [{
+			req: {
+				type: 'object',
+				properties: {
+					emailAddress: { type: 'string' },
+				},
+				required: ['emailAddress'],
+			},
+			res: {
+				type: 'object',
+				properties: {
+					available: { type: 'boolean' },
+					reason: {
+						oneOf: [
+							{ type: 'string', enum: ['used', 'format', 'disposable', 'mx', 'smtp'] },
+							{ type: 'null' },
+						],
+					},
+				},
+				required: [
+					'available',
+					'reason',
+				],
+			},
+		}],
+	},
 } as const satisfies { [x: string]: IEndpointMeta; };
 
 /**