Meridial Marketplace (by Invisible) seeks mathematics experts proficient in Korean to work as freelance AI trainers refining advanced language models. Contributors engage with AI on algebra, calculus, number theory, linear algebra, differential equations, statistics, geometry, mathematical logic, discrete mathematics, real/complex analysis, optimization theory, proofs, set theory, probability, cryptography and applied mathematics, documenting failure modes to strengthen model reasoning. Daily work includes conversing with models on classroom and theoretical problems, verifying accuracy and logic, capturing reproducible errors, and suggesting prompt engineering and evaluation improvements. A Master's or PhD in mathematics or a quantitative field is ideal; peer-reviewed publications, teaching or research experience are valued. Remote worldwide contract paying $6–$65/hour based on experience and location; no company benefits.