An API data flow diagram is a diagram that documents an API's routines and protocols to clarify its structure and behavior. API data flow diagrams are useful because they quickly demonstrate how the system will behave to developers and non-technical stakeholders such as product managers. A flow for an API includes a request, one or more target application actions, and an API operation response. The flow is started by calling the API operation, which can be done from mobile or web applications. A data flow diagram also represents the flow of information through a process or system. It includes data inputs and outputs, data stores, and the various sub-processes the data moves. DFDs describe multiple entities and their relationships using standardized symbols and notation.