## Authentication Model

All endpoints in this specification use **API Key authentication**.

The API key is generated in KlickTipp under:

Listbuilding → New Listbuilding → Entry via API key

Each API key is permanently linked to a specific opt-in process and tag. This defines the scope and behavior of the integration.

Authentication is performed by sending the API key **directly in the request body**. No session handling or cookies are required.

Documentation:
[How to Create an API Key](https://developers.klicktipp.com/guides/listbuilding-api)