diff --git a/packages/express-cargo/src/decorators.ts b/packages/express-cargo/src/decorators.ts
index 8fc4ec5..07f778c 100644
--- a/packages/express-cargo/src/decorators.ts
+++ b/packages/express-cargo/src/decorators.ts
@@ -17,7 +17,7 @@ export function Optional(): PropertyDecorator {
         const classMeta = new CargoClassMetadata(target)
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
         fieldMeta.setOptional(true)
-        fieldMeta.pushAppliedDecorator({ name: Optional.name, category: 'missing-handler' })
+        fieldMeta.pushAppliedDecorator({ name: Optional.name, category: 'missing-handler', args: [] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
     }
 }
@@ -32,7 +32,7 @@ export function List(elementType: ArrayElementType): TypedPropertyDecorator<Arra
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
         const actualType = typeof elementType === 'string' ? TYPE_MAP[elementType] : elementType
         fieldMeta.setArrayElementType(actualType)
-        fieldMeta.pushAppliedDecorator({ name: List.name, category: 'type-helper' })
+        fieldMeta.pushAppliedDecorator({ name: List.name, category: 'type-helper', args: [elementType] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
     }
 }
@@ -46,7 +46,7 @@ export function Default(value: any): PropertyDecorator {
         const classMeta = new CargoClassMetadata(target)
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
         fieldMeta.setDefault(value)
-        fieldMeta.pushAppliedDecorator({ name: Default.name, category: 'missing-handler' })
+        fieldMeta.pushAppliedDecorator({ name: Default.name, category: 'missing-handler', args: [value] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
     }
 }
@@ -91,7 +91,7 @@ export function Type(typeFn: TypeThunk | TypeResolver, options?: TypeOptions): P
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
 
         fieldMeta.setTypeInfo(typeFn, options)
-        fieldMeta.pushAppliedDecorator({ name: Type.name, category: 'type-helper' })
+        fieldMeta.pushAppliedDecorator({ name: Type.name, category: 'type-helper', args: [typeFn, options] })
 
         const designType = Reflect.getMetadata('design:type', target, propertyKey)
         const isArrayType = designType === Array || (typeof designType === 'function' && designType.name === 'Array')
diff --git a/packages/express-cargo/src/enum.ts b/packages/express-cargo/src/enum.ts
index 64db521..b13585a 100644
--- a/packages/express-cargo/src/enum.ts
+++ b/packages/express-cargo/src/enum.ts
@@ -33,7 +33,7 @@ export function Enum<T>(enumObj: any, message?: cargoErrorMessage): TypedPropert
 
         // 1. enum 타입 정보 저장
         fieldMeta.setEnumType(enumObj)
-        fieldMeta.pushAppliedDecorator({ name: Enum.name, category: 'type-helper' })
+        fieldMeta.pushAppliedDecorator({ name: Enum.name, category: 'type-helper', args: [enumObj, message] })
 
         // 2. enum validator 추가
         fieldMeta.addValidator(
diff --git a/packages/express-cargo/src/rules/basic.ts b/packages/express-cargo/src/rules/basic.ts
new file mode 100644
index 0000000..a317c03
--- /dev/null
+++ b/packages/express-cargo/src/rules/basic.ts
@@ -0,0 +1,8 @@
+import { FieldRuleFn } from './types'
+
+const symbolWithoutDescription: FieldRuleFn = s =>
+    typeof s.propertyKey === 'symbol' && !s.propertyKey.description ? `symbol property must have a description` : null
+
+const emptySourceKey: FieldRuleFn = s => (s.hasSource && s.sourceKey === '' ? `@${s.sources[0].name} key must not be an empty string` : null)
+
+export const BASIC_RULES: readonly FieldRuleFn[] = [symbolWithoutDescription, emptySourceKey]
diff --git a/packages/express-cargo/src/rules/crossField.ts b/packages/express-cargo/src/rules/crossField.ts
new file mode 100644
index 0000000..ce5e56a
--- /dev/null
+++ b/packages/express-cargo/src/rules/crossField.ts
@@ -0,0 +1,25 @@
+import { With, Without } from '../validator'
+import { FieldRuleFn, FieldState } from './types'
+
+function unknownReference(state: FieldState, decoratorName: string): string | null {
+    for (const applied of state.appliedSelf) {
+        if (applied.name !== decoratorName) continue
+        const target = applied.args[0]
+        if (typeof target === 'string' && !state.siblingFields.has(target)) {
+            return target
+        }
+    }
+    return null
+}
+
+const withReferencesUnknownField: FieldRuleFn = s => {
+    const target = unknownReference(s, With.name)
+    return target === null ? null : `@With references unknown field "${target}"`
+}
+
+const withoutReferencesUnknownField: FieldRuleFn = s => {
+    const target = unknownReference(s, Without.name)
+    return target === null ? null : `@Without references unknown field "${target}"`
+}
+
+export const CROSS_FIELD_RULES: readonly FieldRuleFn[] = [withReferencesUnknownField, withoutReferencesUnknownField]
diff --git a/packages/express-cargo/src/rules/eachUsage.ts b/packages/express-cargo/src/rules/eachUsage.ts
index 680ffef..5562b9c 100644
--- a/packages/express-cargo/src/rules/eachUsage.ts
+++ b/packages/express-cargo/src/rules/eachUsage.ts
@@ -1,3 +1,5 @@
+import { Each } from '../validator'
+import { isKnownNonArray } from './utils'
 import { FieldRuleFn } from './types'
 
 const eachWrapsSource: FieldRuleFn = s => {
@@ -10,5 +12,7 @@ const eachWrapsMissingHandler: FieldRuleFn = s => {
     return offenders.length === 0 ? null : `@Each cannot wrap missing-handler decorator(s): ${offenders.map(t => `@${t.name}`).join(', ')}`
 }
 
-/** Misuse of `@Each(...)` arguments. */
-export const EACH_USAGE_RULES: readonly FieldRuleFn[] = [eachWrapsSource, eachWrapsMissingHandler]
+const eachOnNonArray: FieldRuleFn = s =>
+    s.appliedSelf.some(d => d.name === Each.name) && isKnownNonArray(s.fieldType) ? `@Each can only be applied to array fields` : null
+
+export const EACH_USAGE_RULES: readonly FieldRuleFn[] = [eachWrapsSource, eachWrapsMissingHandler, eachOnNonArray]
diff --git a/packages/express-cargo/src/rules/registry.ts b/packages/express-cargo/src/rules/registry.ts
index 50a4882..f12e269 100644
--- a/packages/express-cargo/src/rules/registry.ts
+++ b/packages/express-cargo/src/rules/registry.ts
@@ -1,10 +1,19 @@
 import { makeFieldRuleChecker } from './ruleChecker'
 import type { FieldRuleFn, RuleChecker } from './types'
+import { BASIC_RULES } from './basic'
 import { KIND_CATEGORY_RULES } from './kindCategory'
 import { EACH_USAGE_RULES } from './eachUsage'
+import { TYPE_HELPER_PLACEMENT_RULES } from './typeHelperPlacement'
+import { CROSS_FIELD_RULES } from './crossField'
 
 /** All field-level rule implementations currently active. */
-const FIELD_RULES: readonly FieldRuleFn[] = [...KIND_CATEGORY_RULES, ...EACH_USAGE_RULES]
+const FIELD_RULES: readonly FieldRuleFn[] = [
+    ...BASIC_RULES,
+    ...KIND_CATEGORY_RULES,
+    ...EACH_USAGE_RULES,
+    ...TYPE_HELPER_PLACEMENT_RULES,
+    ...CROSS_FIELD_RULES,
+]
 
 /** Single RuleChecker that runs every active field rule. */
 export const ACTIVE_CHECKERS: readonly RuleChecker[] = [makeFieldRuleChecker(FIELD_RULES)]
diff --git a/packages/express-cargo/src/rules/ruleChecker.ts b/packages/express-cargo/src/rules/ruleChecker.ts
index 9bccb51..ba532b5 100644
--- a/packages/express-cargo/src/rules/ruleChecker.ts
+++ b/packages/express-cargo/src/rules/ruleChecker.ts
@@ -7,8 +7,7 @@ import type { FieldRuleFn, FieldState, RuleChecker, RuleViolation } from './type
  * Inspects one class (`ctx.cargoClass`) and returns every violation it finds.
  * Nested-DTO traversal is handled by `validateCargoSchema`, so checkers don't recurse.
  */
-
-function buildFieldState(propertyKey: string | symbol, fieldMeta: CargoFieldMetadata): FieldState {
+function buildFieldState(propertyKey: string | symbol, fieldMeta: CargoFieldMetadata, siblingFields: ReadonlySet<string | symbol>): FieldState {
     const appliedSelf = fieldMeta.getAppliedDecorators('self')
     const appliedEach = fieldMeta.getAppliedDecorators('each')
     const sources = appliedSelf.filter(d => d.category === 'source')
@@ -21,6 +20,8 @@ function buildFieldState(propertyKey: string | symbol, fieldMeta: CargoFieldMeta
         hasSource: sources.length > 0,
         hasRequest: appliedSelf.some(d => d.category === 'request'),
         hasVirtual: appliedSelf.some(d => d.category === 'virtual'),
+        sourceKey: fieldMeta.getKey(),
+        siblingFields,
     }
 }
 
@@ -33,9 +34,11 @@ function buildFieldState(propertyKey: string | symbol, fieldMeta: CargoFieldMeta
 export function makeFieldRuleChecker(rules: readonly FieldRuleFn[]): RuleChecker {
     return ctx => {
         const violations: RuleViolation[] = []
-        for (const propertyKey of ctx.classMeta.getAllFieldsList()) {
+        const fields = ctx.classMeta.getAllFieldsList()
+        const siblingFields = new Set(fields)
+        for (const propertyKey of fields) {
             const fieldMeta = ctx.classMeta.getFieldMetadata(propertyKey)
-            const state = buildFieldState(propertyKey, fieldMeta)
+            const state = buildFieldState(propertyKey, fieldMeta, siblingFields)
             for (const rule of rules) {
                 const message = rule(state)
                 if (message !== null) {
diff --git a/packages/express-cargo/src/rules/typeHelperPlacement.ts b/packages/express-cargo/src/rules/typeHelperPlacement.ts
new file mode 100644
index 0000000..b21e502
--- /dev/null
+++ b/packages/express-cargo/src/rules/typeHelperPlacement.ts
@@ -0,0 +1,11 @@
+import { List, Type } from '../decorators'
+import { isKnownNonArray, isPrimitiveType } from './utils'
+import { FieldRuleFn } from './types'
+
+const listOnNonArray: FieldRuleFn = s =>
+    s.appliedSelf.some(d => d.name === List.name) && isKnownNonArray(s.fieldType) ? `@List can only be applied to array fields` : null
+
+const typeOnPrimitive: FieldRuleFn = s =>
+    s.appliedSelf.some(d => d.name === Type.name) && isPrimitiveType(s.fieldType) ? `@Type cannot be applied to a primitive field` : null
+
+export const TYPE_HELPER_PLACEMENT_RULES: readonly FieldRuleFn[] = [listOnNonArray, typeOnPrimitive]
diff --git a/packages/express-cargo/src/rules/types.ts b/packages/express-cargo/src/rules/types.ts
index ab9a391..1b05c11 100644
--- a/packages/express-cargo/src/rules/types.ts
+++ b/packages/express-cargo/src/rules/types.ts
@@ -17,6 +17,8 @@ export interface FieldState {
     hasSource: boolean
     hasRequest: boolean
     hasVirtual: boolean
+    sourceKey: string | symbol
+    siblingFields: ReadonlySet<string | symbol>
 }
 
 /** A single field-level rule. Returns a violation message, or `null` if the field passes. */
diff --git a/packages/express-cargo/src/rules/utils.ts b/packages/express-cargo/src/rules/utils.ts
new file mode 100644
index 0000000..62ab23e
--- /dev/null
+++ b/packages/express-cargo/src/rules/utils.ts
@@ -0,0 +1,9 @@
+const PRIMITIVE_TYPES: readonly unknown[] = [String, Number, Boolean]
+
+export function isPrimitiveType(fieldType: unknown): boolean {
+    return PRIMITIVE_TYPES.includes(fieldType)
+}
+
+export function isKnownNonArray(fieldType: unknown): boolean {
+    return typeof fieldType === 'function' && fieldType !== Array && fieldType !== Object
+}
diff --git a/packages/express-cargo/src/source.ts b/packages/express-cargo/src/source.ts
index ac117dd..80a3042 100644
--- a/packages/express-cargo/src/source.ts
+++ b/packages/express-cargo/src/source.ts
@@ -13,7 +13,7 @@ function createSourceDecorator(source: Source) {
             const fieldMeta = classMeta.getFieldMetadata(propertyKey)
             fieldMeta.setKey(key ?? propertyKey)
             fieldMeta.setSource(source)
-            fieldMeta.pushAppliedDecorator({ name: source, category: 'source' })
+            fieldMeta.pushAppliedDecorator({ name: source, category: 'source', args: [key] })
             classMeta.setFieldMetadata(propertyKey, fieldMeta)
             classMeta.setFieldList(propertyKey)
         }
diff --git a/packages/express-cargo/src/transform.ts b/packages/express-cargo/src/transform.ts
index d4b11dc..f496950 100644
--- a/packages/express-cargo/src/transform.ts
+++ b/packages/express-cargo/src/transform.ts
@@ -16,7 +16,7 @@ export function Transform<T>(transformer: (value: T) => T): TypedPropertyDecorat
         const classMeta = new CargoClassMetadata(target)
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
         fieldMeta.setTransformer(transformer)
-        fieldMeta.pushAppliedDecorator({ name: Transform.name, category: 'transform' })
+        fieldMeta.pushAppliedDecorator({ name: Transform.name, category: 'transform', args: [transformer] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
     }
 }
@@ -36,7 +36,7 @@ export function Request<T>(transformer: (req: Request) => T): TypedPropertyDecor
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
 
         fieldMeta.setRequestTransformer(transformer)
-        fieldMeta.pushAppliedDecorator({ name: Request.name, category: 'request' })
+        fieldMeta.pushAppliedDecorator({ name: Request.name, category: 'request', args: [transformer] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
         classMeta.setRequestFieldList(propertyKey)
     }
@@ -61,7 +61,7 @@ export function Virtual<T>(transformer: (obj: any) => T): TypedPropertyDecorator
         const fieldMeta = classMeta.getFieldMetadata(propertyKey)
 
         fieldMeta.setVirtualTransformer(transformer)
-        fieldMeta.pushAppliedDecorator({ name: Virtual.name, category: 'virtual' })
+        fieldMeta.pushAppliedDecorator({ name: Virtual.name, category: 'virtual', args: [transformer] })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
         classMeta.setVirtualFieldList(propertyKey)
     }
diff --git a/packages/express-cargo/src/types.ts b/packages/express-cargo/src/types.ts
index 03069ac..4093905 100644
--- a/packages/express-cargo/src/types.ts
+++ b/packages/express-cargo/src/types.ts
@@ -191,6 +191,7 @@ export type DecoratorScope = 'self' | 'each'
 export interface AppliedDecorator {
     name: string
     category: DecoratorCategory
+    args: readonly unknown[]
 }
 
 export type BindSources = {
diff --git a/packages/express-cargo/src/validator.ts b/packages/express-cargo/src/validator.ts
index bcd33a6..b709a7a 100644
--- a/packages/express-cargo/src/validator.ts
+++ b/packages/express-cargo/src/validator.ts
@@ -1,4 +1,5 @@
 import {
+    AppliedDecorator,
     ArrayComparator,
     cargoErrorMessage,
     EachValidatorRule,
@@ -12,10 +13,11 @@ import { CargoClassMetadata } from './metadata'
 import { isDeepEqual } from './utils'
 import { isValidPhoneNumber, CountryCode } from 'libphonenumber-js'
 
-function addValidator(target: any, propertyKey: string | symbol, rule: ValidatorRule) {
+function addValidator(target: any, propertyKey: string | symbol, rule: ValidatorRule, applied?: AppliedDecorator) {
     const classMeta = new CargoClassMetadata(target)
     const fieldMeta = classMeta.getFieldMetadata(propertyKey)
     fieldMeta.addValidator(rule)
+    if (applied) fieldMeta.pushAppliedDecorator(applied)
     classMeta.setFieldMetadata(propertyKey, fieldMeta)
 }
 
@@ -705,6 +707,7 @@ export function With(fieldName: string, message?: cargoErrorMessage): PropertyDe
                 (value: unknown, instance?: Record<string | symbol, any>) => !(!!value && !instance?.[fieldName]),
                 message || `${String(propertyKey)} requires ${fieldName}`,
             ),
+            { name: With.name, category: 'validator', args: [fieldName] },
         )
     }
 }
@@ -728,6 +731,7 @@ export function Without(fieldName: string, message?: cargoErrorMessage): Propert
                 },
                 message || `${String(propertyKey)} cannot exist with ${fieldName}`,
             ),
+            { name: Without.name, category: 'validator', args: [fieldName] },
         )
     }
 }
@@ -943,7 +947,7 @@ export function Each(...args: (PropertyDecorator | TypedPropertyDecorator<any> |
             }
         })
 
-        fieldMeta.pushAppliedDecorator({ name: Each.name, category: 'validator' })
+        fieldMeta.pushAppliedDecorator({ name: Each.name, category: 'validator', args })
         classMeta.setFieldMetadata(propertyKey, fieldMeta)
     }
 }
diff --git a/packages/express-cargo/tests/rules/basic.test.ts b/packages/express-cargo/tests/rules/basic.test.ts
new file mode 100644
index 0000000..15a307d
--- /dev/null
+++ b/packages/express-cargo/tests/rules/basic.test.ts
@@ -0,0 +1,51 @@
+import { Body, CargoSchemaError } from '../../src'
+import { expectViolation, validateCargoSchema } from './testUtils'
+
+describe('schema validation — basic rules', () => {
+    it('rejects a symbol property without a description (A1)', () => {
+        const sym = Symbol()
+
+        class SymbolWithoutDescriptionDto {
+            @Body()
+            [sym]!: string
+        }
+
+        try {
+            validateCargoSchema(SymbolWithoutDescriptionDto)
+        } catch (e) {
+            expect(e).toBeInstanceOf(CargoSchemaError)
+            expect((e as CargoSchemaError).violations.some(v => v.field === sym && v.message.includes('must have a description'))).toBe(true)
+            return
+        }
+        throw new Error('expected CargoSchemaError to be thrown')
+    })
+
+    it('accepts a symbol property with a description', () => {
+        const sym = Symbol('userId')
+
+        class SymbolWithDescriptionDto {
+            @Body()
+            [sym]!: string
+        }
+
+        expect(() => validateCargoSchema(SymbolWithDescriptionDto)).not.toThrow()
+    })
+
+    it('rejects an empty-string source key (A2)', () => {
+        class EmptyKeyDto {
+            @Body('')
+            foo!: string
+        }
+
+        expectViolation(() => validateCargoSchema(EmptyKeyDto), 'foo', 'key must not be an empty string')
+    })
+
+    it('accepts @Body() without an explicit key', () => {
+        class DefaultKeyDto {
+            @Body()
+            foo!: string
+        }
+
+        expect(() => validateCargoSchema(DefaultKeyDto)).not.toThrow()
+    })
+})
diff --git a/packages/express-cargo/tests/rules/crossField.test.ts b/packages/express-cargo/tests/rules/crossField.test.ts
new file mode 100644
index 0000000..ca97a46
--- /dev/null
+++ b/packages/express-cargo/tests/rules/crossField.test.ts
@@ -0,0 +1,41 @@
+import { Body, With, Without } from '../../src'
+import { expectViolation, validateCargoSchema } from './testUtils'
+
+describe('schema validation — cross-field reference rules', () => {
+    it('rejects @With referencing a non-existent field (G1)', () => {
+        class WithUnknownDto {
+            @Body()
+            @With('ghost')
+            foo!: string
+        }
+
+        expectViolation(() => validateCargoSchema(WithUnknownDto), 'foo', '@With references unknown field "ghost"')
+    })
+
+    it('rejects @Without referencing a non-existent field (G2)', () => {
+        class WithoutUnknownDto {
+            @Body()
+            @Without('ghost')
+            foo!: string
+        }
+
+        expectViolation(() => validateCargoSchema(WithoutUnknownDto), 'foo', '@Without references unknown field "ghost"')
+    })
+
+    it('accepts references to existing fields', () => {
+        class CrossFieldValidDto {
+            @Body()
+            bar!: string
+
+            @Body()
+            @With('bar')
+            @Without('baz')
+            foo!: string
+
+            @Body()
+            baz!: string
+        }
+
+        expect(() => validateCargoSchema(CrossFieldValidDto)).not.toThrow()
+    })
+})
diff --git a/packages/express-cargo/tests/rules/eachUsage.test.ts b/packages/express-cargo/tests/rules/eachUsage.test.ts
index d190357..b1cce8c 100644
--- a/packages/express-cargo/tests/rules/eachUsage.test.ts
+++ b/packages/express-cargo/tests/rules/eachUsage.test.ts
@@ -1,8 +1,8 @@
-import { Body, Default, Each, Optional } from '../../src'
+import { Body, Default, Each, Min, Optional } from '../../src'
 import { expectViolation, validateCargoSchema } from './testUtils'
 
 describe('schema validation — @Each usage rules', () => {
-    it('@Each 인자로 Source 데코레이터가 들어가면 거부', () => {
+    it('rejects a source decorator inside @Each (H2)', () => {
         class EachWrapsSourceDto {
             @Body()
             @Each(Body())
@@ -12,7 +12,7 @@ describe('schema validation — @Each usage rules', () => {
         expectViolation(() => validateCargoSchema(EachWrapsSourceDto), 'foo', '@Each cannot wrap source decorator')
     })
 
-    it('@Each 인자로 Missing-Handler 데코레이터(@Optional)가 들어가면 거부', () => {
+    it('rejects @Optional inside @Each (H3)', () => {
         class EachWrapsOptionalDto {
             @Body()
             @Each(Optional())
@@ -22,7 +22,7 @@ describe('schema validation — @Each usage rules', () => {
         expectViolation(() => validateCargoSchema(EachWrapsOptionalDto), 'foo', '@Each cannot wrap missing-handler decorator')
     })
 
-    it('@Each 인자로 Missing-Handler 데코레이터(@Default)가 들어가면 거부', () => {
+    it('rejects @Default inside @Each (H3)', () => {
         class EachWrapsDefaultDto {
             @Body()
             @Each(Default(0))
@@ -31,4 +31,24 @@ describe('schema validation — @Each usage rules', () => {
 
         expectViolation(() => validateCargoSchema(EachWrapsDefaultDto), 'foo', '@Each cannot wrap missing-handler decorator')
     })
+
+    it('rejects @Each on a non-array field (H1)', () => {
+        class EachOnNonArrayDto {
+            @Body()
+            @Each(Min(0))
+            foo!: string
+        }
+
+        expectViolation(() => validateCargoSchema(EachOnNonArrayDto), 'foo', '@Each can only be applied to array fields')
+    })
+
+    it('accepts @Each on an array field', () => {
+        class EachOnArrayDto {
+            @Body()
+            @Each(Min(0))
+            foo!: number[]
+        }
+
+        expect(() => validateCargoSchema(EachOnArrayDto)).not.toThrow()
+    })
 })
diff --git a/packages/express-cargo/tests/rules/typeHelperPlacement.test.ts b/packages/express-cargo/tests/rules/typeHelperPlacement.test.ts
new file mode 100644
index 0000000..d1c4dbf
--- /dev/null
+++ b/packages/express-cargo/tests/rules/typeHelperPlacement.test.ts
@@ -0,0 +1,49 @@
+import { Body, List, Type } from '../../src'
+import { expectViolation, validateCargoSchema } from './testUtils'
+
+class Nested {
+    @Body()
+    value!: string
+}
+
+describe('schema validation — type-helper placement rules', () => {
+    it('rejects @List on a non-array field (M1)', () => {
+        class ListOnNonArrayDto {
+            @Body()
+            @List(Nested)
+            foo!: Nested
+        }
+
+        expectViolation(() => validateCargoSchema(ListOnNonArrayDto), 'foo', '@List can only be applied to array fields')
+    })
+
+    it('accepts @List on an array field', () => {
+        class ListOnArrayDto {
+            @Body()
+            @List(Nested)
+            foo!: Nested[]
+        }
+
+        expect(() => validateCargoSchema(ListOnArrayDto)).not.toThrow()
+    })
+
+    it('rejects @Type on a primitive field (M2)', () => {
+        class TypeOnPrimitiveDto {
+            @Body()
+            @Type(() => Nested)
+            foo!: string
+        }
+
+        expectViolation(() => validateCargoSchema(TypeOnPrimitiveDto), 'foo', '@Type cannot be applied to a primitive field')
+    })
+
+    it('accepts @Type on an object field', () => {
+        class TypeOnObjectDto {
+            @Body()
+            @Type(() => Nested)
+            foo!: Nested
+        }
+
+        expect(() => validateCargoSchema(TypeOnObjectDto)).not.toThrow()
+    })
+})