{
    "description": "Response for extended license usage index action with license units",
    "type": "object",
    "required": [
        "monthly_usage",
        "total_units",
        "usage_by_registration_key"
    ],
    "properties": {
        "monthly_usage": {
            "type": "array",
            "items": {
                "type": "object",
                "required": [
                    "month",
                    "license_units",
                    "unique_clients",
                    "breakdown_by_subject_count"
                ],
                "properties": {
                    "month": {
                        "type": "string",
                        "description": "Month in YYYY-MM format"
                    },
                    "license_units": {
                        "type": "integer",
                        "description": "Total license units consumed in this month"
                    },
                    "unique_clients": {
                        "type": "integer",
                        "description": "Number of unique clients in this month"
                    },
                    "breakdown_by_subject_count": {
                        "type": "object",
                        "description": "Breakdown by number of subjects measured per client",
                        "additionalProperties": {
                            "type": "object",
                            "required": [
                                "clients",
                                "units"
                            ],
                            "properties": {
                                "clients": {
                                    "type": "integer",
                                    "description": "Number of clients with this subject count"
                                },
                                "units": {
                                    "type": "integer",
                                    "description": "License units consumed by clients with this subject count"
                                }
                            }
                        }
                    }
                }
            }
        },
        "total_units": {
            "type": "integer",
            "description": "Total license units across all months"
        },
        "usage_by_registration_key": {
            "type": "array",
            "description": "Per-registration-key breakdown of the license usage. Always present, including when the request is restricted to a single key via registration_key_id, in which case the array contains only that key's entry. Sorted by total_units descending, with the entry for clients without a registration key (registration_key_id: null) always last.",
            "items": {
                "type": "object",
                "required": [
                    "registration_key_id",
                    "registration_key",
                    "comment",
                    "total_units",
                    "total_unique_clients",
                    "monthly_usage"
                ],
                "properties": {
                    "registration_key_id": {
                        "type": "integer",
                        "description": "ID of the registration key. Null for clients registered without a registration key, clients whose registration key has since been deleted, and clients whose own record was deleted since. A non-null id always refers to a key that still exists.",
                        "nullable": true
                    },
                    "registration_key": {
                        "type": "string",
                        "description": "The registration key string. Null when registration_key_id is null.",
                        "nullable": true
                    },
                    "comment": {
                        "type": "string",
                        "description": "Comment/label set on the registration key. Null when registration_key_id is null, or when the key has no comment.",
                        "nullable": true
                    },
                    "total_units": {
                        "type": "integer",
                        "description": "Total license units consumed by this key's clients across all months in the report"
                    },
                    "total_unique_clients": {
                        "type": "integer",
                        "description": "Sum of the unique-client counts across each month for this key (client-months); a client active in multiple months is counted once per month, not once overall"
                    },
                    "monthly_usage": {
                        "type": "array",
                        "description": "Per-month usage for this registration key, covering every month of the report's range with zeros for months without activity",
                        "items": {
                            "type": "object",
                            "required": [
                                "month",
                                "license_units",
                                "unique_clients"
                            ],
                            "properties": {
                                "month": {
                                    "type": "string",
                                    "description": "Month in YYYY-MM format"
                                },
                                "license_units": {
                                    "type": "integer",
                                    "description": "License units consumed by this key's clients in this month"
                                },
                                "unique_clients": {
                                    "type": "integer",
                                    "description": "Number of unique clients belonging to this key that were active in this month"
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}