With the Internet of Things (IoT) paradigm, potentially private data could be made available on the Internet. Such data could then, be consumed by a growing number of applications. The acceptance and success of new pervasive applications depend on both the protection of privacy and the guarantee of quality of context (QoC). As in the IoT producers and consumers of context are decoupled, they are not aware of each other. Therefore, it is essential to provide them with means to express their guarantees and requirements concerning QoC and privacy. For this purpose, we propose meta-models to design context contracts defining privacy and QoC agreements, independently of the consumer and the producer sides. The contracts are key to an autonomous management of QoC and privacy in the IoT. Firstly, contracts may be modified at runtime to add, edit or remove clauses. Secondly, the middleware in charge of transmitting data from context producers to context consumers (e.g., context managers) will be able to match QoC/privacy requirements and guarantees. Finally, the matching process can adapt dynamically, for instance, to the current trust level between the two parties. These contracts will participate to build trust among IoT participants