The YAML file for modified version of the OpenAPI specification for Tado devices is on the link below.

https://github.com/openhab/openhab2-addons/blob/84e5c9be8f54bf9696828bacf0520b7ae77dc94e/bundles/org.openhab.binding.tado/src/main/api/tado-api.yaml

Note: it is subject to a Pull Request to integrate modifications into the openHAB v2 Tado binding, so the link might change after the merge..