Korean grammar, spelling, spacing, and punctuation checker based on standard Korean language rules. Detects and corrects common errors including spelling mistakes (되/돼, -ㄴ지/-는지), spacing errors (의존명사, 보조용언), grammar issues (조사 사용, 시제), and punctuation problems. Use when: (1) Reviewing Korean documents after writing, (2) Real-time correction during writing, (3) Checking Korean comments or documentation in code, (4) Learning Korean grammar with explanations, or (5) Ensuring formal document quality.