JSON Web Tokens (JWTs) are widely used in modern user authentication systems due to their lightweight and portable nature, facilitating secure API calls and single sign-on (SSO). Central to their functionality are JWT claims, which are key–value pairs conveying identity and authorization details. These claims fall into three categories—registered, public, and private—each serving distinct purposes and enabling applications to make access decisions by validating tokens. Proper management of JWT claims is crucial for maintaining security, involving best practices such as validating claims, avoiding storage of sensitive data, and utilizing strong algorithms. Missteps like ignoring expiration checks or misusing private claims can create vulnerabilities. Solutions like Descope simplify the implementation of JWT-based authentication by offering built-in claim validation and workflows, enhancing security while reducing the complexity of customer identity and access management.