A JSON schema describes and validates your existing data format(s). This ensures the quality of client submitted data. MOSP also uses JSON schemas for the generation of the object editor.
For example the JSON schema available here validates the Security referentials used in MONARC. When creating a new object with MOSP you have first to choose a JSON schema.
You can use any available schemas in order to create shareable JSON objects. It is possible to keep an object private even if the goal of this platform is to promote the sharing of information. JSON schemas are always public.