unicorn-mcp

Ultra-efficient Model Context Protocol (MCP) server for the Fast Unicorn commercial boilerplate (premium starter kit on the T3 Stack: Next.js 15 App Router, tRPC 11, Prisma 7, NextAuth v5, Tailwind v4, next-intl, Stripe, Resend).

Compatible with any MCP host: Cursor, Claude Desktop, VS Code (Continue / Cline / Roo), and custom CLIs. Speaks the stdio transport — no HTTP server, no extra config.

What this MCP does

1. Injects a strict system prompt into the IDE's AI the moment it connects. The prompt locks the AI to the boilerplate's conventions (Spanish chat / English code, ~/ imports only, ~/i18n/routing for navigation, tRPC useXxx routers, services receiving the database explicitly).
2. Exposes a read-only tech-stack resource so the AI knows exactly what libraries ship pre-wired (avoids installing duplicates like another toast library when sileo is already there).
3. Ships three deterministic tools the AI can call programmatically.

Surface area (everything the server registers)

| Channel | Name | Purpose | | --- | --- | --- | | initialize | instructions | Canonical system prompt sent on every connect. | | Resource | unicorn-mcp://tech-stack | Pre-installed libraries, conventions, dashboard contract. | | Resource | unicorn-mcp://system-prompt | Mirror of instructions for hosts that ignore it. | | Prompt | system_prompt | One-shot prompt template (use as /system_prompt in some hosts). | | Tool | get_feature_recipe | 6-step recipe to add a new domain (Prisma → service → router → root.ts → i18n → UI). | | Tool | verify_code_compliance | Static analyzer for @/ imports, next/link, NEXTAUTH_SECRET, etc. | | Tool | get_stripe_flow_reference | Canonical Stripe billing pipeline (checkout → webhook → DB sync). |

Tool details

get_feature_recipe

Returns the exact step-by-step Markdown recipe to extend the boilerplate with a brand-new business domain.

• Input: domain (string, e.g. "posts", "orders", "invoices").
• Output: Markdown with the 6 mandatory steps:
  1. Update prisma/schema.prisma → run pnpm db:push or generate a migration.
  2. Write pure business logic under src/server/services/<domain>/, receiving the database client explicitly.
  3. Create the tRPC router under src/server/api/routers/<domain>.ts with the useXxx prefix.
  4. Register it inside appRouter in src/server/api/root.ts.
  5. Add translation namespaces in all three locale files (messages/{en,es,zh}/<domain>.json) and register imports in src/i18n/messages.ts.
  6. Build the localized UI pages under src/app/[locale]/ respecting colocation and using ~/i18n/routing.

verify_code_compliance

Static analysis tool to intercept generated code before writing it to disk.

• Input: code (the snippet) + optional filePath (enables file-specific rules).
• Output: Structured JSON with ok, severity-classified violations, line/column, and a fix suggestion.
• Rules enforced:
  • @/ imports → must be ~/.
  • next/link / next/navigation → must be ~/i18n/routing helpers.
  • emails.ts registered inside src/server/api/root.ts → blocked (it is a "use server" module, not a tRPC router).
  • process.env.NEXTAUTH_SECRET → must be AUTH_SECRET (NextAuth v5 pattern).
  • src/features/ paths → forbidden.
  • Stripe payloads without metadata.userId → flagged as warning.

get_stripe_flow_reference

Returns the canonical architectural map of the Stripe billing flow so the client AI never hallucinates an alternative invoicing pipeline:

1. Client triggers a tRPC mutation (e.g. api.useStripe.upgradeSubscription).
2. tRPC router delegates to services/billing/checkout.ts, which always injects metadata.userId.
3. Stripe Checkout redirects the user to /[locale]/payment/success.
4. Stripe POSTs the asynchronous webhook to /api/stripe/webhook.
5. webhook-sync.ts verifies the STRIPE_WEBHOOK_SECRET signature, extracts metadata.userId, runs idempotency checks, and syncs the active subscription into PostgreSQL.

Install & connect

Published on npm as unicorn-mcp. You do not add it as a dependency of your Next.js app — register it inside your IDE's MCP config and the client runs it with npx.

Cursor / Windows

{
  "mcpServers": {
    "unicorn-mcp": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "unicorn-mcp@latest"]
    }
  }
}

Cursor / macOS / Linux

{
  "mcpServers": {
    "unicorn-mcp": {
      "command": "npx",
      "args": ["-y", "unicorn-mcp@latest"]
    }
  }
}

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "unicorn-mcp": {
      "command": "npx",
      "args": ["-y", "unicorn-mcp@latest"]
    }
  }
}

VS Code (Continue / Cline / Roo, etc.)

Use the IDE's MCP configuration UI and point it at the same npx -y unicorn-mcp@latest command.

How the system prompt reaches the AI

MCP defines three channels through which a server can deliver behavior guidance:

1. instructions field in the response to the initialize request. This is the canonical, host-neutral way. Cursor, Claude Desktop, and Claude Code all forward it as a system message automatically.
2. unicorn-mcp://system-prompt resource for hosts that ignore instructions. The user (or the host) can read the resource manually.
3. system_prompt prompt for hosts that prefer slash-commands (/system_prompt).

unicorn-mcp ships the same text through all three channels so the contract lands no matter the host.

Local development

npm install
npm run dev       # tsx watch src/index.ts
npm run build     # tsc → dist/
npm start         # node dist/index.js (stdio)
npm run typecheck # tsc --noEmit

Code layout

src/
├── index.ts                                # Entry: registers tools, resources, prompts
├── system-prompt.ts                        # Global behavior contract (sent as `instructions`)
├── lib/
│   └── mcp-response.ts                     # Helpers for text/json/markdown MCP responses
├── tools/
│   ├── get-feature-recipe.ts               # `get_feature_recipe` tool
│   ├── verify-code-compliance.ts           # `verify_code_compliance` tool
│   └── get-stripe-flow-reference.ts        # `get_stripe_flow_reference` tool
├── resources/
│   └── boilerplate-tech-stack.ts           # `unicorn-mcp://tech-stack` + `://system-prompt`
└── prompts/
    └── system-prompt.ts                    # `system_prompt` prompt for slash-command hosts

License

MIT.