Written answers in the UPSC mains exam are assessed based on criteria like content richness, structure, originality, relevance, and articulation. Evaluators look for clarity in expression, logical flow of ideas, and adherence to the question's requirements. Factual accuracy and incorporation of relevant examples significantly enhance the quality of answers. Candidates should aim for concise yet comprehensive responses that reflect critical thinking and an integrated approach to various subjects. This assessment approach rewards analytical depth and effective communication, crucial for success.