Django REST Framework Serializer Patterns

Enforces DRF serializer best practices with Input/Output separation, field-level validation, and proper read_only/write_only configuration. Auto-activates on: serializer, validation, DRF, input/output, field-level, read_only, write_only, nested serializer. Prevents single serializer for both I/O, business logic in serializers, missing validation, incorrect field configuration. Ensures separate Input/Output serializers, validate_<field> methods, proper read_only_fields, nested serializer optimization. Targets: 100% I/O separation, comprehensive validation, optimized nested serializers.