A migratable agent, which has the function of providing an interface between the user and the devices with which it needs to interact, can provide the user with continuous assistance. The relationship established between a human and the agent would enable the user to operate home appliances smoothly. However, few studies which have addressed the primary questions that arise in this regard; for example, how and when the agent should execute the task requested by the user. This paper proposes the use of a design principle based on the BDI model for a migratable agent to ensure that it is capable of carrying out user's tasks appropriately. The BDI model enables the agent to determine the scope of continuing actions to achieve its intended target. The BDI model allows the agent to execute tasks in the clear range of achieving intentions and guarantees the completion of tasks within a reasonable range. We investigated the validity of adopting the BDI model by obtaining feedback via questionnaires related to the design of the migratable agent. The results of the questionnaires indicated that the BDI model would be able to facilitate the design of the migratable agent.