Gemini controlled generation no longer supports schema fields that previously worked

[adesso-dominik-chodounsky]

I am using Gemini's controlled generation function in one of my projects.
I use an OpenAPI schema with Vertex AI fields.

For one attribute, I had the following definition:
{"type": "string", "format": "date", "example": "2015-12-04"} which worked a few weeks ago, but currently results in:
InvalidArgument : 400 Unable to submit request because one or more response schemas specified unsupported field example.

If I remove the fields format and example, the whole generation works.

I cannot find release notes that would describe a change in this anywhere, did the support for this change? Both fields are specified in the Vertex AI Schema docs: https://cloud.google.com/vertex-ai/docs/reference/rest/v1/Schema,
but on the Controlled Generation page, they are largely limited: http://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/control-generated-output#considerations