generate-youtube-thumbnail

これはレビュー時に保存された抜粋です。完全で最新の内容は外部ソースを確認してください。

---
name: generate-youtube-thumbnail
description: >-
  Generate high-CTR YouTube thumbnails using Nano Banana 2 via the Arcads external API. Handles reference image upload, character likeness alignment, proven CTR-tested prompt formulas, and parallel batch generation. Use when the user asks to create a YouTube thumbnail, video thumbnail, A/B test thumbnail variations, or refers to thumbnail design with their face, brand assets, or product photos.
---

# Generate YouTube Thumbnail

A reusable workflow for creating YouTube thumbnails via Arcads' Nano Banana 2 image endpoint with proper character likeness and proven CTR formulas.

## When to use this skill

Trigger on phrases like:
- "make me a YouTube thumbnail"
- "create a thumbnail for this video"
- "I need thumbnail variations / A/B tests"
- "remake this thumbnail with my face"
- "generate 10 thumbnail concepts"
- "thumbnail with [me / my product / my brand]"

## Read order

1. **This file** — workflow, decision tree, batch generation
2. **[shared/skills/generate-youtube-thumbnail/prompting/guide.md](../../shared/skills/generate-youtube-thumbnail/prompting/guide.md)** — likeness alignment, expressions cheat sheet, prompt structure (shared across all generative-AI APIs in this portfolio)
3. **[shared/skills/generate-youtube-thumbnail/prompting/formulas.md](../../shared/skills/generate-youtube-thumbnail/prompting/formulas.md)** — 5 proven thumbnail formulas with templates (shared)
4. **[scripts/generate-batch.sh](scripts/generate-batch.sh)** — Arcads-specific batch script (presigned upload + S3 PUT pipeline)

## Prerequisites

- `.env` with `ARCADS_BASIC_AUTH` and `ARCADS_API_KEY`
- A `productId` (defaults to MASTER_CONTEXT.md's "My workspace" product)
- Reference images on disk (NOT pasted in chat — chat-pasted images are NOT accessible to the API):
  - `face/` — 5+ photos of the subject (headshot + 3/4 angles + close-ups + expressions)
  - `logos/` — brand logos as files (orange Claude Code starburst, black Arcads A, etc.)
  - `products/` — clean product shots
  - `examples/` — real ad screenshots, comparison material
  - `style/` — example thumbnails the user wants to match aesthetically

If references are missing or the user pastes images in chat instead of saving them, **stop and ask the user to drop the actual files into a project folder** (e.g. `references/youtube thumbnail/`). Chat paste ≠ file on disk.

## Workflow

### 1. Gather requirements (in order)

Ask the user for any missing context, but only what you actually need:

1. **Concept** — what's the video about? Single concept, A/B variations, or specific recreation of an existing thumbnail style?
2. **Subject** — who is in the thumbnail (the user themselves, an AI character, no person)?
3. **Brand assets** — which logos / products / brand colors should appear?
4. **Text** — what should the title text say? Will text be baked in, or added in post (Canva/Photoshop)?
5. **Comparison material** — for "real vs AI" thumbnails, what real ad and what AI-generated ad?

### 2. Verify references exist on disk

```bash
ls "references/youtube thumbnail/"
```

If references are missing, ask the user to drop them. **Do not proceed with text-only descriptions for brand-specific items** (logos, branded products, branded apparel) — you'll get generic AI approximations that don't match the brand. Generic descriptions are OK for backgrounds, expressions, and clothing.

### 3. Estimate cost and confirm

Always present cost as an **estimate** before firing:

> "Estimated cost: N variations × 24 credits = X credits. Tell me if you want to confirm exact pricing in the Arcads platform first."

### 4. Pick a formula

See **[shared/skills/generate-youtube-thumbnail/prompting/formulas.md](../../shared/skills/generate-youtube-thumbnail/prompting/formulas.md)** for the 5 proven formulas. Match the user's intent:

| User says... | Use formula |
|---|---|
| "Just me with my brand" / "branding thumbnail" | **Peace-sign / branding** |
| "Real vs AI"