Sumaki is a wrapper for structured data like JSON. Since Sumaki wraps the target data as it is, rather than parsing it using a schema, the original data can be referenced at any time. This makes it easy to add or modify definitions as needed while checking the target data. This feature may be useful when there is no document defining the structure of the data, or when the specification is complex and difficult to grasp, and the definition is written little by little starting from the obvious places.