The Web is populated by multiple and heterogeneous online systems. When aiming at supporting users with tasks on the Web, intelligent agents should be able to access these systems in a seamless and regulated way. Our approach to tackle the accessibility challenge has two facets. First, we introduce a knowledge layer structured along the Multi-Agent Oriented Programming approach to comprehensively describe the system’s resources and regulations using ontology. Second, we illustrate the use of this knowledge layer with an agent reasoning and acting in compliance with the system’s regulations towards achieving its goals. We use online forum as the domain application to highlight the applicability and usefulness of our approach.