diff --git a/packages/backend/src/misc/schema.ts b/packages/backend/src/misc/schema.ts
index 212d0f7ec724..6a0802f8a408 100644
--- a/packages/backend/src/misc/schema.ts
+++ b/packages/backend/src/misc/schema.ts
@@ -136,18 +136,19 @@ type PartialIntersection<T> = Partial<UnionToIntersection<T>>;
 // https://github.com/misskey-dev/misskey/pull/8144#discussion_r785287552
 // To get union, we use `Foo extends any ? Hoge<Foo> : never`
 type UnionSchemaType<a extends readonly any[], X extends Schema = a[number]> = X extends any ? SchemaType<X> : never;
-type UnionObjectSchemaType<a extends readonly any[], X extends Schema = a[number]> = X extends any ? ObjectSchemaType<X> : never;
+//type UnionObjectSchemaType<a extends readonly any[], X extends Schema = a[number]> = X extends any ? ObjectSchemaType<X> : never;
+type UnionObjType<s extends Obj, a extends readonly any[], X extends ReadonlyArray<keyof s> = a[number]> = X extends any ? ObjType<s, X> : never;
 type ArrayUnion<T> = T extends any ? Array<T> : never;
 
 type ObjectSchemaTypeDef<p extends Schema> =
 	p['ref'] extends keyof typeof refs ? Packed<p['ref']> :
 	p['properties'] extends NonNullable<Obj> ?
 		p['anyOf'] extends ReadonlyArray<Schema> ? p['anyOf'][number]['required'] extends ReadonlyArray<keyof p['properties']> ?
-			ObjType<p['properties'], NonNullable<p['anyOf'][number]['required']>> & ObjType<p['properties'], NonNullable<p['required']>>
+			UnionObjType<p['properties'], NonNullable<p['anyOf'][number]['required']>> & ObjType<p['properties'], NonNullable<p['required']>>
 			: never
 			: ObjType<p['properties'], NonNullable<p['required']>>
 	:
-	p['anyOf'] extends ReadonlyArray<Schema> ? UnionObjectSchemaType<p['anyOf']> & PartialIntersection<UnionObjectSchemaType<p['anyOf']>> :
+	p['anyOf'] extends ReadonlyArray<Schema> ? never : // see CONTRIBUTING.md
 	p['allOf'] extends ReadonlyArray<Schema> ? UnionToIntersection<UnionSchemaType<p['allOf']>> :
 	any
 
diff --git a/packages/backend/src/server/api/endpoints/admin/drive/show-file.ts b/packages/backend/src/server/api/endpoints/admin/drive/show-file.ts
index 85b566aabe57..1d27ac213716 100644
--- a/packages/backend/src/server/api/endpoints/admin/drive/show-file.ts
+++ b/packages/backend/src/server/api/endpoints/admin/drive/show-file.ts
@@ -138,19 +138,13 @@ export const meta = {
 
 export const paramDef = {
 	type: 'object',
+	properties: {
+		fileId: { type: 'string', format: 'misskey:id' },
+		url: { type: 'string' },
+	},
 	anyOf: [
-		{
-			properties: {
-				fileId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['fileId'],
-		},
-		{
-			properties: {
-				url: { type: 'string' },
-			},
-			required: ['url'],
-		},
+		{ required: ['fileId'] },
+		{ required: ['url'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/drive/files/show.ts b/packages/backend/src/server/api/endpoints/drive/files/show.ts
index e0a07a36401f..271b33ef4b0b 100644
--- a/packages/backend/src/server/api/endpoints/drive/files/show.ts
+++ b/packages/backend/src/server/api/endpoints/drive/files/show.ts
@@ -39,19 +39,13 @@ export const meta = {
 
 export const paramDef = {
 	type: 'object',
+	properties: {
+		fileId: { type: 'string', format: 'misskey:id' },
+		url: { type: 'string' },
+	},
 	anyOf: [
-		{
-			properties: {
-				fileId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['fileId'],
-		},
-		{
-			properties: {
-				url: { type: 'string' },
-			},
-			required: ['url'],
-		},
+		{ required: ['fileId'] },
+		{ required: ['url'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts b/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
index bcd793ac4349..da1a4bcc46ed 100644
--- a/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
+++ b/packages/backend/src/server/api/endpoints/notes/search-by-tag.ts
@@ -36,32 +36,25 @@ export const paramDef = {
 		sinceId: { type: 'string', format: 'misskey:id' },
 		untilId: { type: 'string', format: 'misskey:id' },
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
-	},
-	anyOf: [
-		{
-			properties: {
-				tag: { type: 'string', minLength: 1 },
-			},
-			required: ['tag'],
-		},
-		{
-			properties: {
-				query: {
-					type: 'array',
-					description: 'The outer arrays are chained with OR, the inner arrays are chained with AND.',
-					items: {
-						type: 'array',
-						items: {
-							type: 'string',
-							minLength: 1,
-						},
-						minItems: 1,
-					},
-					minItems: 1,
+
+		tag: { type: 'string', minLength: 1 },
+		query: {
+			type: 'array',
+			description: 'The outer arrays are chained with OR, the inner arrays are chained with AND.',
+			items: {
+				type: 'array',
+				items: {
+					type: 'string',
+					minLength: 1,
 				},
+				minItems: 1,
 			},
-			required: ['query'],
+			minItems: 1,
 		},
+	},
+	anyOf: [
+		{ required: ['tag'] },
+		{ required: ['query'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/pages/show.ts b/packages/backend/src/server/api/endpoints/pages/show.ts
index 651252afbbfa..bf2b2a431e85 100644
--- a/packages/backend/src/server/api/endpoints/pages/show.ts
+++ b/packages/backend/src/server/api/endpoints/pages/show.ts
@@ -29,20 +29,14 @@ export const meta = {
 
 export const paramDef = {
 	type: 'object',
+	properties: {
+		pageId: { type: 'string', format: 'misskey:id' },
+		name: { type: 'string' },
+		username: { type: 'string' },
+	},
 	anyOf: [
-		{
-			properties: {
-				pageId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['pageId'],
-		},
-		{
-			properties: {
-				name: { type: 'string' },
-				username: { type: 'string' },
-			},
-			required: ['name', 'username'],
-		},
+		{ required: ['pageId'] },
+		{ required: ['name', 'username'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/users/followers.ts b/packages/backend/src/server/api/endpoints/users/followers.ts
index 17ce92001155..97f1310c3601 100644
--- a/packages/backend/src/server/api/endpoints/users/followers.ts
+++ b/packages/backend/src/server/api/endpoints/users/followers.ts
@@ -46,25 +46,18 @@ export const paramDef = {
 		sinceId: { type: 'string', format: 'misskey:id' },
 		untilId: { type: 'string', format: 'misskey:id' },
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+
+		userId: { type: 'string', format: 'misskey:id' },
+		username: { type: 'string' },
+		host: {
+			type: 'string',
+			nullable: true,
+			description: 'The local host is represented with `null`.',
+		},
 	},
 	anyOf: [
-		{
-			properties: {
-				userId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['userId'],
-		},
-		{
-			properties: {
-				username: { type: 'string' },
-				host: {
-					type: 'string',
-					nullable: true,
-					description: 'The local host is represented with `null`.',
-				},
-			},
-			required: ['username', 'host'],
-		},
+		{ required: ['userId'] },
+		{ required: ['username', 'host'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/users/following.ts b/packages/backend/src/server/api/endpoints/users/following.ts
index 6dbda0d72f1a..d406594a2e20 100644
--- a/packages/backend/src/server/api/endpoints/users/following.ts
+++ b/packages/backend/src/server/api/endpoints/users/following.ts
@@ -46,25 +46,18 @@ export const paramDef = {
 		sinceId: { type: 'string', format: 'misskey:id' },
 		untilId: { type: 'string', format: 'misskey:id' },
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+
+		userId: { type: 'string', format: 'misskey:id' },
+		username: { type: 'string' },
+		host: {
+			type: 'string',
+			nullable: true,
+			description: 'The local host is represented with `null`.',
+		},
 	},
 	anyOf: [
-		{
-			properties: {
-				userId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['userId'],
-		},
-		{
-			properties: {
-				username: { type: 'string' },
-				host: {
-					type: 'string',
-					nullable: true,
-					description: 'The local host is represented with `null`.',
-				},
-			},
-			required: ['username', 'host'],
-		},
+		{ required: ['userId'] },
+		{ required: ['username', 'host'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/users/search-by-username-and-host.ts b/packages/backend/src/server/api/endpoints/users/search-by-username-and-host.ts
index 1cefcf2707ea..6c340d8fb292 100644
--- a/packages/backend/src/server/api/endpoints/users/search-by-username-and-host.ts
+++ b/packages/backend/src/server/api/endpoints/users/search-by-username-and-host.ts
@@ -31,20 +31,13 @@ export const paramDef = {
 	properties: {
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
 		detail: { type: 'boolean', default: true },
+
+		username: { type: 'string', nullable: true },
+		host: { type: 'string', nullable: true },
 	},
 	anyOf: [
-		{
-			properties: {
-				username: { type: 'string', nullable: true },
-			},
-			required: ['username'],
-		},
-		{
-			properties: {
-				host: { type: 'string', nullable: true },
-			},
-			required: ['host'],
-		},
+		{ required: ['username'] },
+		{ required: ['host'] },
 	],
 } as const;
 
diff --git a/packages/backend/src/server/api/endpoints/users/show.ts b/packages/backend/src/server/api/endpoints/users/show.ts
index 70258ef00926..29f24b045a24 100644
--- a/packages/backend/src/server/api/endpoints/users/show.ts
+++ b/packages/backend/src/server/api/endpoints/users/show.ts
@@ -54,32 +54,22 @@ export const meta = {
 
 export const paramDef = {
 	type: 'object',
-	anyOf: [
-		{
-			properties: {
-				userId: { type: 'string', format: 'misskey:id' },
-			},
-			required: ['userId'],
-		},
-		{
-			properties: {
-				userIds: { type: 'array', uniqueItems: true, items: {
-					type: 'string', format: 'misskey:id',
-				} },
-			},
-			required: ['userIds'],
-		},
-		{
-			properties: {
-				username: { type: 'string' },
-				host: {
-					type: 'string',
-					nullable: true,
-					description: 'The local host is represented with `null`.',
-				},
-			},
-			required: ['username'],
+	properties: {
+		userId: { type: 'string', format: 'misskey:id' },
+		userIds: { type: 'array', uniqueItems: true, items: {
+			type: 'string', format: 'misskey:id',
+		} },
+		username: { type: 'string' },
+		host: {
+			type: 'string',
+			nullable: true,
+			description: 'The local host is represented with `null`.',
 		},
+	},
+	anyOf: [
+		{ required: ['userId'] },
+		{ required: ['userIds'] },
+		{ required: ['username'] },
 	],
 } as const;