Written communication skills are crucial for the UPSC Mains since candidates must express their thoughts clearly and concisely in essays and answers. Effective writing not only reflects a candidate's knowledge but also their ability to organize ideas logically. Poor communication can lead to misinterpretation of responses, affecting overall scores. Thus, mastering written communication is vital for providing insightful answers that resonate with the evaluators. Candidates should practice writing regularly to enhance fluency and coherence in their responses.