Pinterest carousel Pins: multiple_image_urls takes 2 to 5 images

A carousel Pin in the Pinterest v5 API uses a media source of type multiple_image_urls with an items array of 2 to 5 images. Each item can carry its own title, description and link. To fill one from AI imagery, generate five matching frames with the same model and aspect_ratio, host them, and pass their URLs.

What does the media source look like?

The spec defines PinMediaSourceImagesURL with a source_type of multiple_image_urls and an items array with minItems: 2 and maxItems: 5. Each item has the image URL plus optional title, description and link fields. A base64 variant, multiple_image_base64, exists alongside it.

How do I generate a coherent set?

Reuse the model, the style words and the aspect_ratio for every frame, and change only the subject. Use 2:3 if the Pin should fill the feed. Run the requests with separate prompts and keep the results in order.

import json, os, urllib.request

body = {
    "model": "bytedance-seed/seedream-4.5",
    "prompt": "step 1 of 5, whisking eggs in a blue bowl, overhead, bright kitchen, flat illustration",
    "aspect_ratio": "2:3",
    "output_format": "jpeg"
}
req = urllib.request.Request(
    "https://api.sume.com/v1/images",
    data=json.dumps(body).encode(),
    headers={
        "Authorization": "Bearer " + os.environ["SUME_API_KEY"],
        "Content-Type": "application/json",
    },
    method="POST",
)
print(urllib.request.urlopen(req).read().decode())

What goes wrong?

• Fewer than 2 or more than 5 items: the schema rejects the array.
• Frames with mixed ratios: the carousel looks uneven.
• Private or expiring URLs: Pinterest must fetch each one, so use stable hosting.
• Per-item text beyond the field limits: keep titles near the 100-character Pin title cap.

Where should I look next?

The images guide covers Sume's side; Pinterest's spec holds the item field limits.