Fetching fixed and variable costs for a contract

A contract's costs are made up of billing items, each of which is either:

  • Fixed (subscription) — a periodic charge independent of usage

  • Variable (consumption) — a usage-based charge tied to a unit of measure, billed per Gj/kWh/m³/...

The model chain is:

Contract
  └─ BillingDetails.Products[]        (per-period product references)
       └─ Product.BillingItems[]      (billing items attached to the product)
            └─ BillingItem.CalculationParameters   ("subscription" = fixed | "consumption" = variable)
                 └─ BillingTariff       (the € amount — UnitTariff)

Steps

Step 1 — Get the contract

GET /api/md/contracts/{contractUuid}

API documentation

Returns a ContractDTO.
The field you need:

  • BillingDetails.Products[]

Take every (currently active, or period-relevant) ProductId from BillingDetails.Products[] into step 2.

Step 2 — Get each product's billing items

GET /api/cfg/products/{productUuid}

API documentation

Returns a ProductDTO with BillingItems[] (ProductBillingItemDTO) — each entry gives you a BillingItemId plus its PeriodicityParameters.
Collect every BillingItemId.

Step 3 — Get each billing item (fixed vs. variable happens here)

GET /api/cfg/billingitems/{billingItemUuid}

API documentation

Returns a BillingItemDTO with Name, Description, and a polymorphic CalculationParameters, discriminated by JSON "type".
Bucket each billing item as fixed (type: "subscription") or variable (type: "consumption") based on this field.

Step 4 — Get the tariff (the € amount)

GET /api/cfg/billingtariffs?productId={productUuid}&billingItemId={billingItemUuid}

API documentation

Returns BillingTariffDTO[] with a polymorphic CalculationParameters.
The common case is:

{
    "id": "c412...",
    "productId": "...",
    "billingItemId": "b1a7...",
    "contractId": null,
    "startDateTime": "2026-01-01T00:00:00Z",
    "endDateTime": null,
    "calculationParameters": {
        "type": "unitPrice",
        "unitTariff": 32.80
    }
}

unitTariff is the € amount per unit — per year for a subscription billing item, per unit of measure (e.g. per Gj) for a consumption billing item.

Tariffs can be contract-specific: if a tariff's contractId matches your contract, prefer it over a generic product-level tariff (contractId: null) for the same billing item.

Other calculation types exist besides unitPrice — tiered, volume, stairStep, condition — each with its own parameter shape in the same response family. Handle unitPrice first; the others are needed only if the contract uses tiered/volume-based pricing.