# Beatra Skill + MCP — Interpolate first and last frames

> Generate one continuous motion path between controlled endpoints.
> Self-contained workflow guide for AI agents.
> Human-readable page: https://docs.beatra.ai/en/docs/capabilities/videos/frames-to-video

- Primary surface: the Universal Beatra Skill with authenticated MCP.
- Install or reconnect: https://beatra.ai/install.md
- MCP endpoint: `https://mcp.beatra.ai/mcp`
- Billable action: `beatra.videos.interpolate`
- Dynamic model facts: call `beatra.models.list` with `capability: "frames_to_video"` only when model constraints, controls, or prices matter.
- Interaction model: create one opaque `client_request_id`, submit the finalized arguments exactly once, then poll the returned `task_id` with `beatra.tasks.get` until terminal.
- Local media: call `beatra.assets.upload`, perform the returned HTTPS PUT exactly, and use the artifact ID from the PUT response.

REST/OpenAPI is the fallback protocol path, not the primary agent packaging.

---

## Primary agent path

Use `beatra.videos.interpolate` only when both a first and last image define the
transition. Preserve their order.

1. Upload both local frames and optional driving audio.
2. Call `beatra.models.list` with `capability: "frames_to_video"` for current
   media combinations, duration, resolution, audio support, and prices.
3. Describe the movement between the endpoints, not two disconnected scenes.
4. Submit once with one `client_request_id`; poll with `beatra.tasks.get`.

## Tool arguments

```json
{
  "prompt": "The product rises and rotates smoothly between the two views",
  "first_frame": { "type": "artifact", "artifact_id": "artifact_start" },
  "last_frame": { "type": "artifact", "artifact_id": "artifact_end" },
  "driving_audio": { "type": "artifact", "artifact_id": "artifact_optional_audio" },
  "resolution": "720p",
  "duration": 6,
  "client_request_id": "vid-frames-opaque-1"
}
```

Omit `driving_audio` when it is unsupported or unnecessary. Image-driven
aspect-ratio rules come from model discovery.

## Models, controls, and cost

Common controls are `prompt`, `negative_prompt`, `resolution`,
`duration`, `aspect_ratio`, `seed`, `enhance_prompt`, and `watermark`.
Use each only according to the selected model's metadata.

Use `beatra.models.list` instead of a static model table. It returns selectable
models, accepted frame/audio combinations, constraints, defaults, ignored
fields, and customer prices. Resolution and duration normally affect cost; do
not silently change them.

### MiniMax H3

Set `model: "minimax-h3"` to interpolate with MiniMax H3. Both frames and a
prompt are required. Output is 2K, duration is 4–15 seconds, and the first
frame determines the output ratio. H3 accepts `watermark` but not driving
audio or the other optional controls. Both input images are free and generated
output costs 590 credits per second.

## Task status and recovery

Poll the same task through `queued` and `running`. A lost create response may be
retried only with identical arguments and the same `client_request_id`.
Swapping either frame or changing audio, prompt, or output settings requires a
new ID.

## REST API

Direct protocol integrations may use `POST /v1/videos/frames-to-video`. Follow
the generated [API operation](https://docs.beatra.ai/en/docs/api-reference/operations/videos/videos_f2v_v1_videos_frames_to_video_post).
Skill + MCP is the recommended integration; REST serves custom applications.

---

## Appendix: shared Skill + MCP contract

### Retry identity

One logical generation has one `client_request_id`. If the create response is
lost, retry the exact same arguments with that ID. If any prompt, media, model,
or output control changes, use a new ID. Never create another paid task merely
because the first task is `queued` or `running`.

### Polling and billing truth

Poll with `beatra.tasks.get` using bounded backoff. Stop at `succeeded`,
`failed`, or `canceled`. Only the task response is authoritative for the
resolved model, artifacts, charged credits, and refunded credits.

### Recovery

Preserve structured Beatra error codes. Reconnect on authentication failure;
stop and request a balance action on insufficient balance; refresh current
constraints with `beatra.models.list` after model validation; request a new
upload grant after expiration or MIME/length mismatch. Changed generation
arguments always require a new `client_request_id`.