Bring your REST/OpenAPI, we expose authenticated MCP + JPY billing + インボイス invoices + analytics — the JP-localised alternative to Smithery/Composio.

Source signals

• **SIG-20260425-japan-api-as-a-product-personal-mcp-server-pattern** — "JP devs MCP-ifying utilities one-by-one because no JP-localised platform exists; explicit DIY pattern."
• **SIG-20260425-japan-api-as-a-product-jp-public-api-mcp-wrapper** — "Puente charges ¥150-500K/mo for the unified MCP wrapper around JP public APIs; WTP validated."
• **SIG-20260425-japan-api-as-a-product-claude-code-token-explosion** — "Claude Code adoption explosion in JP dev community drives MCP demand."
• **SIG-20260425-japan-api-as-a-product-salesforce-headless-api-trend** — "Headless / API-first / MCP trend across enterprise."

Reasoning

This is a meta-trend play: 4+ independent posts on Qiita/Zenn in 2 weeks all describe the same DIY pattern, and parallel global moves (Microsoft APM, Google agents-cli, Copilot CLI) confirm MCP is consolidating as the standard. The white space is specifically JP-localised payment compliance + Japanese onboarding — Smithery's biggest moat-gap. Stack is simple (FastAPI + Postgres + Redis + Stripe + custom 適格請求書 generator + MCP runtime per tenant), 12 days. AI auto-conversion (OpenAPI→MCP via Claude Sonnet) is both onboarding-magic and a hard-to-copy AI layer. Risk window is short — Smithery/Composio could localise, or MCP standard could consolidate around one player — but first-mover JP advantage (developer trust, distribution channels, 適格請求書 compliance) is durable. WTP is bimodal: indie devs at ¥2K/mo subscriptions, enterprise innovation labs at ¥30-100K/mo for white-label.

Quick competitive read

• **Smithery (smithery.ai)** — direct global competitor, EN/USD-only, no インボイス compliance.
• **Composio** — same EN/USD profile.
• **Microsoft APM / Google agents-cli / Copilot CLI** — enterprise MCP-management, not marketplace.
• **Self-hosted DIY** — what we replace (4+ Qiita posts as evidence).
• JP-localised MCP marketplace with JPY billing + インボイス: **no direct competitor**, **white space**, `competitive_pressure: 7-9`. Window may close fast.

Initial pricing hypothesis

Free (1 tool, 1K calls/mo, our branding), Maker ¥2K/mo (5 tools, 50K calls, custom branding), Pro ¥10K/mo (unlimited + 500K calls + webhooks + SLA + white-label), Enterprise ¥50K+/mo (on-prem + SOC2-style controls). 10-20% markup on publisher per-call price.

Distribution hypothesis

Qiita/Zenn long-form Japanese guides ("publish your first MCP server and earn ¥10K in a week") — 6-8 posts month one; Tokyo hackathon sponsorships (AI agent meetups, AI Tokyo); cold-DM on Twitter/X to 100 JP devs publishing MCP tutorials; partnerships with Japanese VC communities (NoCode Camp, IndieHackers Japan) for credibility and distribution.

What we ship

**Core features (MVP)**

• Publisher portal for MCP servers — JP-localised dashboard: GitHub OAuth → upload OpenAPI spec or git-clone URL → Claude Sonnet 4.6 auto-converts to an MCP server config (tools, schemas, auth) → preview → publish; per-tenant deployment in an isolated Railway runtime. From "I have a REST API" to "I have a paid MCP tool" in five minutes.
• JPY billing + 適格請求書 issuer auto-registration — Stripe in JPY mode + custom 適格請求書 (qualified invoice) generator with 13-digit T-number; the **適格請求書発行事業者 registration wizard** is built into onboarding (renders required forms, drafts the 申請書, walks through e-Tax submission). Single biggest moat against Smithery/Composio.
• Security review badge after the Smithery incident — every MCP server gets an auto-scan for path-traversal, secret leaks, and known CVEs; manual review on Pro+ tier; badge surfaces on the marketplace and in the consumer's dashboard. Direct response to the October 2025 Smithery breach (3,000+ servers exposed).
• 特定商取引法 disclosure + JP-developer onboarding — mandatory 特定商取引法 disclosure page on the publisher dashboard; JP-language onboarding flow (Qiita-style tutorials inline); automatic 消費税 (8/10%) calculation via Stripe Tax.
• Per-tenant MCP runtime + analytics — every publisher gets an isolated FastAPI tenant (Postgres row-level + Redis namespace), real-time analytics (calls/day, top consumers, revenue), webhooks on new subscriptions.

**Primary user flow**

1. Developer onboarding (publisher persona) — GitHub OAuth → wizard "Got an OpenAPI spec? Git repo? Just a REST endpoint?" → upload/paste → Claude Sonnet auto-converts to MCP config → preview tools + schemas → click "Publish" → MCP server live on `https://{publisher}.mcp-jp.dev` in five minutes.

2. 適格請求書 issuer registration wizard — after first billing setup, onboarding step "register as 適格請求書発行事業者 with 税務署" delivers a pre-filled 申請書 PDF, e-Tax submission walkthrough, deadline tracker (needed before the first JPY invoice).

3. Consumer side (AI-agent dev) — consumer finds the MCP server in the JP marketplace, sees the "Security Reviewed" badge, JPY pricing, 適格請求書 support → subscribes → MCP endpoint appears in their Claude/agent setup → every AI call is metered through our platform.

4. Billing — Free (1 tool, 1K calls/mo, our branding) → Maker ¥2K/mo (5 tools, 50K calls, custom branding) → Pro ¥10K/mo (unlimited + 500K calls + webhooks + SLA + white-label) → Enterprise ¥50K+/mo (on-prem + SOC2-style controls). 10-20% markup on the publisher's per-call price.

**What it looks like**

• Landing page (developer-friendly, in Japanese): hero "あなたのAPIを5分で課金可能なMCPに — JPY/適格請求書対応の唯一のMCPホスティング", live demo (drag OpenAPI YAML → MCP preview), comparison vs Smithery (no JPY, no 適格請求書, Oct 2025 breach) and Composio (EN-only), JPY pricing table, "Security Reviewed" badge demo, JP indie-dev testimonials.
• API docs page (developer SDK): bilingual EN/JP, MCP protocol reference, "Bring your OpenAPI" quickstart, security best practices (post-Smithery), webhook payload examples, white-label customisation guide.
• Publisher dashboard: list of published MCP servers with status (Draft / Reviewed / Live / Suspended), revenue graph (¥/day), top consumers, per-server security-scan results, webhook delivery log, 適格請求書 issuer registration status with countdown, 特定商取引法 disclosure editor.
• JPY billing screen: PDF preview of the outbound 適格請求書 for the consumer (T1234567890123, 消費税 10%, 振込先, total in yen); inbound monthly Stripe receipt for the publisher (our revenue share); freee/MFクラウド export for the contador.

**MVP build plan: 12 days**

• Day 1-2: FastAPI + Postgres + Redis + Stripe (JPY mode), GitHub OAuth, scaffolded publisher dashboard.
• Day 3-4: OpenAPI→MCP auto-converter (Claude Sonnet 4.6 prompt + schema validator), preview UI.
• Day 5-6: Per-tenant MCP runtime (isolated FastAPI workers per publisher on Railway), auth, metering.
• Day 7: 適格請求書 (qualified invoice) generator with 13-digit T-number, custom PDF template; Stripe Tax integration for 消費税 (8/10%).
• Day 8: 適格請求書発行事業者 registration wizard (税務署 申請書 generator + e-Tax walkthrough + deadline tracker).
• Day 9: Security review pipeline (auto-scan for path-traversal, secret leaks, CVEs) + "Security Reviewed" badge UI.
• Day 10: 特定商取引法 disclosure page editor + analytics dashboard (revenue, calls, top consumers).
• Day 11: Webhook delivery (Resend), white-label customisation for Pro tier.
• Day 12: Marketplace listing UI (consumer side) + soft launch — Qiita post + 5 indie-dev pilots.