The development of an open system which consists of distributed cooperative agents needs some special attentions in the software engineering cycle. Because of the openness and the cooperation between applications (i.e., the software agents), the validation of the model is more and more urgent. But the characteristics of the system, like the distribution of the applications over networks, make it impossible to validate within a local system by a test execution and debugging. The integration of a formal validation technique into the development of such systems also influences the other software life cycles, for example the modeling and the implementation. In this paper we analyze the general concerns in developing cooperative agents in an open environment, and the difficulties in integrating a formal validation in it. We have implemented a component based environment for developing agents in three phases of software life cycle. The SCD language has been developed to model the agent behavior which is encapsulated within a mobile agent structure. A part of the agent model is translated into the colored Petri net model for the purpose of formal validation. In the selected example, we have modeled, using the SCD language, the agents who communicate through the contract net protocol, and visualized the exchanged messages within the mobile agent platforms. We have validated their conversation protocol using the CPN/AMI tool for certain properties like deadlock freeness, live-lock freeness or the reachability, etc. In the conclusion, we evaluate our approach considering the three software development phases: i) Componential modeling, ii) model transformation and formal validation, and iii) java source code generation and implementation within mobile agent platforms.