Every year, embedded systems, such as self-driving systems, are becoming larger and more complex which requires high computing power yet low power consumption. To meet these requirements, there is an increase in the usage of many-core processors. However, thorough understanding of the concept of many-core processors is needed for these to be adopted. Therefore, Software-Hardware Interface for Multi-Many-Core (SHIM), a hardware abstraction description, was developed to reduce the burden on developers. However, SHIM cannot fully demonstrate communication overhead as it describes overhead in instruction units. For this reason, the communication overhead cannot be used to estimate execution time. With this, we propose a new schema that can describe the communication overhead in API units. In other words, the communication API overhead can be described without relying on communication libraries. To improve the usability of the existing schema, which is SHIM, we incorporated the proposed schema into SHIM. We set up what is required of the proposed schema, considered use cases, and actually created instance diagrams to evaluate the proposed schema. We also compared the proposed schema with SHIM and determined what needs to be modified when incorporating the schema. As a result, the proposed schema can express communication overhead that varies with the combination of cores and message size, while significantly reducing the amount of description.