GET /v1/models and filter type: "image" for the live list and prices. A few starting points:
Fields that apply across models:
prompt, negative_prompt, aspect_ratio, generate_image_count.
Model-specific ones (quality tiers, resolution, formats) are listed with their allowed values and
a ready-to-send example_request in GET /v1/models/{id} and on each page under Image models;
sending a value the model does not accept is a 422 before any charge.
Prompting advice for specific models lives on ekly.ai, for example the
Kling prompting guide.