GOBL defines all structures in Go and uses the jsonschema package to automatically convert them into valid JSON Schema. For example, take the following Message struct found inside the GOBL note package: 
// Message represents the minimum possible contents for a GoBL document type. This is
// mainly meant to be used for testing purposes.
type Message struct {
	// Summary of the message content
	Title string `json:"title,omitempty" jsonschema:"title=Title"`
	// Details of what exactly this message wants to communicate
	Content string `json:"content" jsonschema:"title=Content"`
	// Any additional semi-structured data that might be useful.
	Meta org.Meta `json:"meta,omitempty" jsonschema:"title=Meta Data"`
}
When converted to JSON Schema, it takes the following form: 
{
  "$schema": "http://json-schema.org/draft/2020-12/schema",
  "$id": "https://gobl.org/draft-0/note/message",
  "$ref": "#/$defs/Message",
  "$defs": {
    "Message": {
      "properties": {
        "title": {
          "type": "string",
          "title": "Title",
          "description": "Summary of the message content"
        },
        "content": {
          "type": "string",
          "title": "Content",
          "description": "Details of what exactly this message wants to communicate"
        },
        "meta": {
          "patternProperties": {
            ".*": {
              "type": "string"
            }
          },
          "type": "object",
          "title": "Meta Data",
          "description": "Any additional semi-structured data that might be useful."
        }
      },
      "type": "object",
      "required": ["content"],
      "description": "Message represents the minimum possible contents for a GoBL document type."
    }
  },
  "$comment": "Generated with GOBL v0.18.0"
}