Japanese Spec Kit — Idea to 5 Definition Docs
What this skill does
Drop a one-line app idea in Japanese and get five aligned definition documents — written in Japanese, structured for a Japanese development team, ready to hand off.
The skill runs as a pipeline:
- You provide: a one-sentence app idea (e.g. "中小企業向けのSaaS契約管理ツールを作りたい")
- The skill asks: 3–5 targeted clarifying questions (target users, scale, integration constraints)
- You receive: 5 internally-consistent Markdown documents
The 5 documents
| Document | Japanese name | What's inside |
|---|---|---|
| Requirements | 要求定義書 | User personas, jobs-to-be-done, business goals, success metrics |
| Functional Spec | 要件定義書 | Feature list, user flows, screen specs, acceptance criteria |
| Technical Design | 技術定義書 | Architecture, stack rationale, data model, API design, Mermaid diagrams |
| Project Plan | 工程定義書 | Milestones, dependencies, estimated timeline, team composition |
| Quality Plan | 品質定義書 | Test strategy, KPIs, monitoring, release criteria |
Each document references the others — no rewriting the same assumptions five times.
Built-in stack assumptions
Pre-tuned for the stack that dominates Japanese product startups:
- Frontend: Next.js (App Router) + TypeScript
- Backend: Python (FastAPI) or TypeScript (Bun / Hono)
- Infra: Google Cloud Run, Cloud SQL, Cloud Storage
- Auth: Firebase Auth or Auth.js
- AI/Agent layer: Anthropic Claude API, optional MCP servers
You can override any of these in clarifying questions — the skill adapts.
Who this is for
- Startup CTOs drafting specs before their first engineering hire
- Product managers translating ideas into developer-ready specs
- Contract developers (受託開発) needing a fast first-draft spec for client review
- In-house DX teams at non-tech companies starting an internal tool project
- Consultants producing upstream documentation deliverables
What you get
- 5 Markdown files (one per definition document)
- Mermaid diagrams embedded inline (renders in Notion, GitHub, GitLab, VS Code)
- Internal cross-references between documents
- Ready to paste into Notion / GitHub / Cursor
What this skill is NOT
- Not a code generator — it produces specs, not working code
- Not for non-Japanese projects — all output is in Japanese
- Not a one-shot prompt — it asks clarifying questions to ground the output in your actual context
- Not a substitute for product discovery — it accelerates documentation, not customer research
FAQ
Q: Can I edit the output before using it?
A: Yes, output is plain Markdown — edit freely in any text editor.
Q: What if my stack isn't Next.js / Python?
A: Tell the skill in the clarifying-question phase. It will adapt to Go, Rails, Java, etc.
Q: How long does generation take?
A: Typically 5–10 minutes end-to-end including clarification turns.
Q: Is the output good enough to send to a client?
A: It's a strong first draft. Review and edit before client delivery — but expect to save 80%+ of the writing time.
