In Flowlet, schemas are used, for example, when defining input for REST endpoints and validating request bodies, among many other use cases. The format for this schema is a subset of JSON Schema, with the addition of an "id" type that also adds the property "references" to declare that the property contains an id to the referenced object. This is especially useful in database tables because it lets you pick the referenced object instead of copy-pasting ids.
A schema editor is available to inspect and edit schemas in the Flowlet interface, as shown in the screenshot.
There is a link "Generate or input" available. You can use this to generate the schema based on JSON data or export/import from JSON Schema. It is recommended that you import from JSON schema when you have it since it contains more information, for example, which properties are required and which aren't. However, a JSON schema is often not available. The generator makes an intelligent guess on the schema based on the provided input data, but you should always check its output. Especially, give attention to additional properties and the required flags.