Bug Report: Incorrect exports Configuration Prevents Import of Submodules #70

Summary:
The exports configuration in @modelcontextprotocol/sdk's package.json causes import issues for submodules like @modelcontextprotocol/sdk/client. This results in TypeScript being unable to resolve the module without additional paths configuration in tsconfig.json.

Steps to Reproduce:

1. Create a new project:

   mkdir temp-test
   cd temp-test
   npm init -y
   npm install @modelcontextprotocol/sdk

2. Add a minimal tsconfig.json:

   {
     "compilerOptions": {
       "module": "ESNext",
       "target": "ES6",
       "moduleResolution": "node",
       "strict": true
     }
   }

3. Create a test.ts file:

   import { Client } from "@modelcontextprotocol/sdk/client";
   
   console.log("test");

4. Compile the project:

   npx tsc

Expected Behavior:

The submodule @modelcontextprotocol/sdk/client should resolve correctly without requiring additional TypeScript configuration.

Actual Behavior:

TypeScript fails with the following error:

Cannot find module '@modelcontextprotocol/sdk/client' or its corresponding type declarations.

The issue can be worked around by adding the following to tsconfig.json:

"paths": {
  "@modelcontextprotocol/sdk/*": ["node_modules/@modelcontextprotocol/sdk/dist/*"]
},
"baseUrl": ".",

However, this should not be necessary.

Root Cause Analysis:

The package.json of @modelcontextprotocol/sdk includes the following exports configuration:

"exports": {
  "./*": "./dist/*"
}

It does not explicitly map @modelcontextprotocol/sdk/client. As a result, TypeScript cannot resolve the submodule.

Suggested Fix:

Update the exports field in package.json to include explicit mappings for submodules. For example:

"exports": {
  "./*": "./dist/*",
  "./client": "./dist/client/index.js",
  "./client/stdio": "./dist/client/stdio/index.js"
}

Environment:

• Node.js: v16.0.0+
• TypeScript: v4.9.0+
• OS: OSX