ESM module resolution fails: Cannot find module './tools/index'

[Nik-Kras]

I tried to connect the MCP to Claude Code and it failed with ERR_MODULE_NOT_FOUND

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/path/to/node_modules/@cmd8/excalidraw-mcp/dist/tools/index' imported from /path/to/node_modules/@cmd8/excalidraw-mcp/dist/index.js

Probably the bug happened because of a mismatch between development tooling and Node.js runtime requirements

// This works in bundlers, fails in Node.js ESM:                                         
import { foo } from './utils/helper'                                                     
                                                                                       
// Node.js ESM requires:                                                                 
import { foo } from './utils/helper.js'

Root Cause

The package has an ESM configuration mismatch:

1. package.json has "type": "module" (ESM mode)
2. tsconfig.json uses "moduleResolution": "bundler" which allows extensionless
   imports
3. tsc compiles the TypeScript without adding .js extensions
4. Node.js ESM requires explicit .js extensions for relative imports