# Happy Horse (`happy_horse`)

> Alibaba video generation. Expressive character motion.

- Capability: Video (tool `video`) — Text to video, Image to video, Video to video
- Price: from $0.42 per run (1 credit = $0.01). Exact price for a request: POST https://api.varg.ai/v2/estimate
- Typical time: ~3 min
- JSON Schema: https://api.varg.ai/v2/tools/video?model=happy_horse (public, no key)
- Try it: https://varg.ai/dashboard/tools/playground?model=happy_horse

## Call it

REST: `POST https://api.varg.ai/v2/tools/video/call` with `Authorization: Bearer $VARG_API_KEY` (create a key at https://varg.ai/dashboard/api).
It answers `202` with a job right away. Poll `GET /v2/jobs/{id}` until `status` is `completed`, then read `output.outputs[0].url` — or pass `options.webhook_url` and get the finished job POSTed to you.

```bash
curl -X POST https://api.varg.ai/v2/tools/video/call \
  -H "Authorization: Bearer $VARG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "happy_horse",
  "prompt": "a cute cat playing with a ball of yarn in a sunny garden, cinematic",
  "aspect_ratio": "16:9",
  "duration": 5
}'
```

MCP: the varg server `https://mcp.varg.ai/mcp` (OAuth sign-in, no key) runs it with `call_tool`:

```json
{
  "tool": "video",
  "input": {
    "model": "happy_horse",
    "prompt": "a cute cat playing with a ball of yarn in a sunny garden, cinematic",
    "aspect_ratio": "16:9",
    "duration": 5
  },
  "wait": true
}
```

## Inputs

| field | type | required | default | allowed | description |
|---|---|---|---|---|---|
| `model` | string | yes | — | `happy_horse` or a route key below | Which model runs the job. |
| `prompt` | string | no | — | — | — |
| `files` | array of { url } | no | — | — | — |
| `aspect_ratio` | string | no | — | e.g. 16:9 \| 9:16 \| 1:1 \| 4:3 \| 3:4 \| 21:9 \| auto | — |
| `resolution` | string | no | — | 480p \| 720p \| 1080p \| 4k | Quality tier. Supported by this model: 720p, 1080p. Unsupported tiers fall back to the nearest available. |
| `audio` | boolean | no | — | — | Native audio track request. Not supported by this model — ignored if sent. |
| `duration` | integer | no | — | 3–15 | Length in seconds. Supported by this model's routes: fal: integer 3-15. A non-numeric value such as "auto" is routed to a route whose schema accepts it; when none does, the request is rejected. |

Media inputs are URLs. Upload a local file first with `POST /v2/files` and pass the returned URL.

## Provider options

Optional, per provider, under `provider_options.<provider>`. Only the options of the provider that runs the job apply — pin a route to choose it.

### provider_options.fal

| field | type | required | default | allowed | description |
|---|---|---|---|---|---|
| `prompt` | string | no | — | — | Text prompt describing the desired video. Max 2500 characters. |
| `image_urls` | array of URL strings | no | — | — | — |
| `reference_image_urls` | array of URL strings | no | — | — | — |
| `seed` | integer | no | — | 0–2147483647 | Random seed for reproducibility |
| `duration` | integer | no | — | 3–15 | Output video duration in seconds (3-15) |
| `resolution` | string | no | — | 720p \| 1080p | — |
| `aspect_ratio` | string | no | — | 16:9 \| 9:16 \| 1:1 \| 4:3 \| 3:4 | — |
| `enable_safety_checker` | boolean | no | — | — | Enable content moderation for input and output |
| `image_url` | string (URL) | no | — | — | URL of the first frame image. Formats: JPEG, JPG, PNG, BMP, WEBP. Dimensions must be at least 300px. Aspect ratio must be between 1:2.5 and 2.5:1. Max 10 MB. |
| `video_url` | string (URL) | no | — | — | URL of the source video to edit. Formats: MP4, MOV (H.264 recommended). Duration: 3-60 s. Longer side <= 2160 px, shorter side >= 320 px. Aspect ratio between 1:2.5 and 2.5:1. Frame rate > 8 fps. Max 100 MB. The output video preserves the source aspect ratio. Output duration matches the input video, capped at 15 s (longer inputs are truncated to the first 15 s). |
| `audio_setting` | string | no | — | auto \| origin | — |

## Routes

`"model": "happy_horse"` picks a route automatically (priority order, then the inputs you send). To pin one, pass its key as `model`.

| model key | provider | modality | price from | typical time |
|---|---|---|---|---|
| `fal:alibaba/happy-horse/text-to-video` | fal | text-to-video | $0.42 | ~3 min |
| `fal:alibaba/happy-horse/image-to-video` | fal | image-to-video | $0.42 | ~3 min |
| `fal:alibaba/happy-horse/reference-to-video` | fal | image-to-video | $0.42 | ~3 min |
| `fal:alibaba/happy-horse/video-edit` | fal | video-to-video | $0.84 | ~3 min |

## Example output

- video/mp4: https://s3.varg.ai/files/ee388aea-c8c3-41de-9345-24881cc87757/file_c67b7a413856.mp4

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Catalog version 2026-11-11T12:59:09.901887+00:00. All models: https://varg.ai/models/llms.txt