The MPEG-21 Media Contract Ontology (MCO), a part of the standard ISO/IEC 21000, is an ontology to represent contracts dealing with rights on multimedia assets and intellectual property protected content in general. A core model provides the elements to describe the permissions, obligations and prohibitions exchanged in the clauses of a contract. Specific vocabulary is defined in a model extension to represent the most common rights and constraints in the audiovisual context. Design principles, a methodology and a comparative analysis are given, as well as the practical guidelines to use the standard. A thorough description of the contract creation workflow from an original contract is given, including a sample contract text, the RDF version, the detailed mapping of the most relevant clauses and the reconstructed version. A set of MCO-related tools is described, including (i) the reference software to create and edit MCO contracts; (ii) modules to identify, store, search, validate and deliver MCO contracts and (iii) a tool to convert between the akin Contract Expression Language (CEL) contracts and the MCO contracts and (iv) the actual use of MCO in the Rightsdraw family of services.