Cloud computing is considered as important aspect for assessing various services. There are many cloud service providers that makes provision of different services and consumers that acquire these services by mentioning requirements. Agents are required to interact with consumers and providers in order to make service negotiation decisions. Provider has to make decisions regarding which cloud service requests to accept based on availability of its resources by evaluating current demands for services as well as future demands. Agent-based approach is mainly concerned with design and development of such agents to help discover various services, negotiate with providers and consumers and composition of cloud services. The novel contributions include developing an agent-based service discovery engine, effectively adopting service negotiation methodology and composing cloud services in unified, single window solution. Service discovery agent consults ontology system for similarity reasoning and negotiation mechanism can be established between consumers and brokers for cloud service markets and between brokers and providers for cloud resource markets. The proposed system provides higher probability of getting the resources.