Leanmcp Builder Skill

This skill guides you in building MCP servers using the Leanmcp SDK - a decorator-based TypeScript framework for elegant MCP development.

When to Use This Skill

• User asks for "leanmcp server"
• User wants "MCP with decorators"
• User needs "authenticated MCP server"
• User wants "simpler MCP development"
• User mentions "@leanmcp/core"
• User needs "user input collection" or "elicitation"
• User wants "environment injection" for multi-tenant secrets

Leanmcp vs Vanilla MCP

Feature	Vanilla MCP	Leanmcp SDK
Tool definition	Manual schema	@Tool decorator with auto-schema
Input validation	Manual	Automatic with @SchemaConstraint
Service discovery	Manual registration	Auto-discovery from ./mcp directory
Authentication	DIY	@Authenticated decorator
User input	Not built-in	@Elicitation decorator
Secrets	DIY	@RequireEnv + getEnv()

Core Packages

# Minimal setup
npm install @leanmcp/core

# With authentication
npm install @leanmcp/auth

# With user input forms
npm install @leanmcp/elicitation

# With user secrets
npm install @leanmcp/env-injection

# CLI (global or dev)
npm install -g @leanmcp/cli

Project Structure

my-leanmcp-server/
├── main.ts                 # Entry point (minimal)
├── mcp/                    # Auto-discovered services
│   ├── example/
│   │   └── index.ts        # Exports ExampleService
│   └── myservice/
│       └── index.ts        # Exports MyService
├── package.json
├── tsconfig.json
└── .env

Required package.json