The growing adoption of the Service Oriented Architecture (SOA) for provisioning services and the proliferation of Internet-enabled handheld devices are changing the services landscape. Users are increasingly demanding services that can adapt to their current context. In this paper, we propose a framework for provisioning context information to adaptive services. The framework relies on negotiated Context Level Agreements (CLAs) between context-consumers (adaptive services) and context-providers by means of a context broker. The CLA specifies the context information and the agreed upon level of quality-of-context (QoC) that the context-provider shall deliver. We describe the components of the framework and the CLA negotiation process. One of the advantages of the approach is that context-providers can provide several types of context information at different QoC levels. Moreover, the publish/subscribe model allows the broker to be aware of significant variations in QoC offerings; and consequently, be able to monitor the execution of CLAs.