Clarify role of Swagger plugin and class-validator in validation

Author: KarthikRaju391

content/openapi/cli-plugin.md

@@ -53,6 +53,10 @@ export class CreateUserDto {
 }
 ```
 
+> info **Note** The Swagger plugin will derive the @ApiProperty() annotations from the TypeScript types and class-validator decorators. This helps in clearly describing your API for the generated Swagger UI documentation. However, the validation at runtime would still be handled by class-validator decorators. So, it is required to continue using validators like `IsEmail()`, `IsNumber()`, etc.
+
+Hence, if you intend to relay on automatic annotations for generating documentations and still wish for runtime validations, then the class-validator decorators are still necessary.
+
 > info **Hint** When using [mapped types utilities](https://docs.nestjs.com/openapi/mapped-types) (like `PartialType`) in DTOs import them from `@nestjs/swagger` instead of `@nestjs/mapped-types` for the plugin to pick up the schema.
 
 The plugin adds appropriate decorators on the fly based on the **Abstract Syntax Tree**. Thus you won't have to struggle with `@ApiProperty` decorators scattered throughout the code.