input can hold a list of parts. Check architecture.input_modalities of the model in /v1/models: a part the model cannot read fails with 400 unsupported_modality.
One inline part can be up to 20 MiB and the whole request up to 32 MiB.
Models that draw return an
image_generation_call output item with the image in result and its type in mime_type. To edit that image on the next turn, send the item back in input.