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

[rtuin]

I'm getting this error on a very basic Client implementation of @modelcontextprotocol/sdk on node 20 and 22.

Reproduction script:

import { Client } from '@modelcontextprotocol/sdk/client';
import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio';
import { ListResourcesResultSchema } from '@modelcontextprotocol/sdk/types';

const run = async () => {
 const transport = new StdioClientTransport({
 command: 'npx @modelcontextprotocol/postgres-server postgres://....',
 });

 const client = new Client(
 {
 name: 'example-client',
 version: '1.0.0',
 },
 { capabilities: {} }
 );

 await client.connect(transport);

 const resources = await client.request({ method: 'resources/list' }, ListResourcesResultSchema);
 console.log(resources);
};

run();

Is this a known issue? Any thoughts on how to get this example working?

[jspahrsummers]

The MCP library exports only ESM modules, which have to be imported with their file extensions, like:

import { Client } from '@modelcontextprotocol/sdk/client/index.js';

Does that work for you?

Separately, note that this won't work—you'll have to move everything after npx here to args:

command: 'npx @modelcontextprotocol/postgres-server postgres://....',

[tyre]

I was also banging my head against this last night. Why does the example in the README show normal package imports while it only works (at least for me locally) when digging into the library for the specific file?

[rtuin]

The MCP library exports only ESM modules, which have to be imported with their file extensions, like:

import { Client } from '@modelcontextprotocol/sdk/client/index.js';

Does that work for you?

Yes, that's it, thanks.
I've updated the docs accordingly.