What Does Self-Describing Message Mean?
A self-describing message contains the data and metadata describing the format and meaning of a message. They usually contain all the data needed to understand the message, and all the information necessary to complete a task. Self-describing messages help in reducing the amount of coupling between components throughout the system, and in facilitating independent evolution of client-server components.
Techopedia Explains Self-Describing Message
A self-describing message may include syntax and semantics, an Extensible Markup Language (XML) is an example of a self-describing message containing tag and value pairs. Essentially, self-describing messages contain both the metadata describing the message schema, and the values that correspond to the schema.