Use RunComfy's API to run blackforestlabs/flux-3/first-last-frame-to-video. For accepted inputs and outputs, see the model's schema.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-3/first-last-frame-to-video \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"start_image_url": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-start.webp",
"end_image_url": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-end.webp",
"prompt": "He grips the rope tightly on the dock, then moves beside the boat as the camera follows in one continuous shot. Soft harbor water and distant gulls."
}'Set the YOUR_API_TOKEN environment variable with your API key (manage keys in your Profile) and include it on every request as a Bearer token via the Authorization header: Authorization: Bearer $YOUR_API_TOKEN.
Submit an asynchronous generation job and immediately receive a request_id plus URLs to check status, fetch results, and cancel.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-3/first-last-frame-to-video \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"start_image_url": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-start.webp",
"end_image_url": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-end.webp",
"prompt": "He grips the rope tightly on the dock, then moves beside the boat as the camera follows in one continuous shot. Soft harbor water and distant gulls."
}'Fetch the current state for a request_id ("in_queue", "in_progress", "completed", or "cancelled").
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/status \
--header "Authorization: Bearer <token>"Retrieve the final outputs and metadata for the given request_id; if the job is not complete, the response returns the current state so you can continue polling.
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/result \
--header "Authorization: Bearer <token>"Cancel a queued job by request_id; in-progress jobs cannot be cancelled.
curl --request POST \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/cancel \
--header "Authorization: Bearer <token>"Provide a publicly reachable HTTPS URL. Ensure the host allows server-side fetches (no login/cookies required) and isn't rate-limited or blocking bots. Recommended limits: images ≤ 50 MB (~4K), videos ≤ 100 MB (~2–5 min @ 720p). Prefer stable or pre-signed URLs for private assets.
{
"type": "object",
"title": "Input schema",
"required": [
"start_image_url",
"end_image_url",
"prompt"
],
"properties": {
"start_image_url": {
"title": "Start Image URL",
"description": "URL of the image used as the first frame of the video (PNG, JPEG, or WebP).",
"type": "string",
"default": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-start.webp"
},
"end_image_url": {
"title": "End Image URL",
"description": "URL of the image used as the last frame of the video (PNG, JPEG, or WebP).",
"type": "string",
"default": "https://playgrounds-storage-public.runcomfy.net/tools/7398/media-files/ref-promo-end.webp"
},
"prompt": {
"title": "Prompt",
"description": "The text prompt describing the video you want to generate.",
"type": "string",
"default": "He grips the rope tightly on the dock, then moves beside the boat as the camera follows in one continuous shot. Soft harbor water and distant gulls."
},
"aspect_ratio": {
"title": "Aspect Ratio",
"description": "Aspect ratio of the generated video. auto lets the model choose.",
"type": "string",
"enum": [
"auto",
"21:9",
"2:1",
"16:9",
"4:3",
"1:1",
"3:4",
"9:16"
],
"default": "16:9"
},
"resolution": {
"title": "Resolution",
"description": "Resolution of the generated video.",
"type": "string",
"enum": [
"720p",
"1080p"
],
"default": "720p"
},
"duration": {
"title": "Duration",
"description": "Duration of the generated video in seconds. An explicit duration is required to place the end frame.",
"type": "integer",
"enum": [
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20
],
"default": 5
},
"generate_audio": {
"title": "Generate Audio",
"description": "Whether to generate audio for the video.",
"type": "boolean",
"default": true
},
"safety_tolerance": {
"title": "Safety Tolerance",
"description": "The safety tolerance level for the generated video. 0 is the strictest and 4 is the most permissive.",
"type": "integer",
"minimum": 0,
"maximum": 4,
"default": 2
}
}
}{
"output": {
"type": "object",
"properties": {
"image": {
"type": "string",
"format": "uri",
"description": "single image URL"
},
"video": {
"type": "string",
"format": "uri",
"description": "single video URL"
},
"images": {
"type": "array",
"description": "multiple image URLs",
"items": {
"type": "string",
"format": "uri"
}
},
"videos": {
"type": "array",
"description": "multiple video URLs",
"items": {
"type": "string",
"format": "uri"
}
}
}
}
}RunComfy is the premier ComfyUI platform, offering ComfyUI online environment and services, along with ComfyUI workflows featuring stunning visuals. RunComfy also provides AI Models, enabling artists to harness the latest AI tools to create incredible art.