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TypeScript Configuration

MCPKit uses TypeScript decorators extensively. This requires specific TypeScript settings to work correctly.

Required Configuration​

Create or update your tsconfig.json:

{
  "compilerOptions": {
    // Required for decorators
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,

    // Recommended settings
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",

    // Strict mode (recommended)
    "strict": true,
    "strictPropertyInitialization": false,

    // Output
    "outDir": "dist",
    "declaration": true,

    // Other useful settings
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist"]
}

Understanding the Settings​

experimentalDecorators​

Enables the experimental decorator syntax used by @MCPServer, @Tool, @Resource, etc.

emitDecoratorMetadata​

Emits design-type metadata for decorated declarations. This allows MCPKit to infer parameter types automatically.

target: "ES2022"​

ES2022 includes all the features MCPKit needs, including:

  • Top-level await
  • Class fields
  • Private class members

module: "NodeNext"​

Uses Node.js's native ESM resolution, which is the modern standard for Node.js packages.

Common Issues​

"Decorators are not enabled"​

Make sure experimentalDecorators is set to true in your tsconfig.json.

"Unable to infer types"​

Ensure emitDecoratorMetadata is true. Without this, MCPKit can't automatically infer parameter types.

Import Errors​

If you see ESM/CJS import errors, ensure:

  1. module is set to "NodeNext"
  2. Your package.json has "type": "module"
  3. Imports include the .js extension (even for .ts files)

Example Project Structure​

my-server/
├── package.json
├── tsconfig.json
├── src/
│   ├── index.ts
│   └── server.ts
└── dist/
    ├── index.js
    └── server.js

package.json​

{
  "name": "my-mcp-server",
  "version": "1.0.0",
  "type": "module",
  "main": "dist/index.js",
  "scripts": {
    "build": "tsc",
    "start": "node dist/index.js",
    "dev": "tsx watch src/index.ts"
  },
  "dependencies": {
    "@mcpkit-dev/core": "^2.0.0",
    "reflect-metadata": "^0.2.0",
    "zod": "^3.0.0"
  },
  "devDependencies": {
    "typescript": "^5.0.0",
    "tsx": "^4.0.0"
  }
}
Required Import

Always import reflect-metadata at the top of your entry file before any other imports:

import 'reflect-metadata';
import { createServer, MCPServer, Tool, Param } from '@mcpkit-dev/core';

This is required for TypeScript decorators to work properly.