How does client-facing documentation rigorously distinguish between a security *recommendationand a security *requirementfor OTP integration?

Client-facing documentation rigorously distinguishes between a security recommendation and a security requirement for One-Time Password (OTP) integration primarily through precise terminology, explicit consequences, and clear contextualization within the document structure. A security *requirementis a mandatory, non-negotiable control or specification that *mustbe implemented for the OTP integration to function correctly, achieve baseline security, or meet specific compliance, regulatory, or policy obligations. Failure to meet a requirement typically results in the integration being unfeasible, insecure, non-compliant, or non-functional. Documentation identifies requirements using imperative verbs and phrases such as "MUST," "SHALL," "REQUIRED," "MANDATORY," "MUST NOT," or "PROHIBITED." For instance, a requirement might state: "The OTP generation algorithm SHALL adhere to RFC 6238 (TOTP) standards, employing a cryptographically secure hash function." This indicates that using any other algorithm or a weak hash function would render the integration unacceptable. The documentation often explicitly states the direct consequence of not fulfilling a requirement, such as "Failure to implement this control will prevent system certification" or "Non-compliance with this requirement will result in a security vulnerability that blocks integration." Requirements are often directly tied to auditability and a foundational security posture. A security *recommendation*, conversely, is an advisory best practice or suggested enhancement that, while highly encouraged for improved security, resilience, or user experience, is not strictly mandatory for the basic functionality or initial integration. Not implementing a recommendation typically does not prevent the integration from working, but it may leave the system vulnerable to advanced threats, reduce its robustness, or lead to a suboptimal user experience. Documentation conveys recommendations using less strict language such as "SHOULD," "SHOULD NOT," "RECOMMENDED," "OPTIONAL," "MAY," or "CONSIDER." For example, a recommendation might advise: "Clients SHOULD implement a robust rate-limiting mechanism for OTP validation attempts to mitigate brute-force attacks." This suggests that while OTP validation would still technically function without rate-limiting, the system would be at a significantly higher risk of compromise. The documentation often explains the security benefit of following the recommendation, such as "Implementing this mechanism reduces the risk of credential stuffing and account takeover." The implications of not following a recommendation are framed as potential risks or decreased resilience, rather than outright failure or non-compliance. Furthermore, the structural organization of documentation reinforces this distinction, often by dedicating separate sections or clearly marked subsections for "Mandatory Requirements" versus "Recommended Best Practices" or "Security Enhancements," providing distinct contexts for each category.