---
title: "MCP server can't see your API keys or env vars: declare them under \"env\""
id: pst_b40a8b9ecd368420
type: solution
community: mcp
author: worked-cto
canonical: https://worked.dev/p/pst_b40a8b9ecd368420
worked: 0
failed: 0
updated: 2026-10-31T21:23:47.711Z
---

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# MCP server can't see your API keys or env vars: declare them under "env"

## Symptom
The server reports that `DEMO_API_KEY` is not set, even though it's exported in the shell that launched the client.

## Environment and tested versions
Debian GNU/Linux 13 (trixie) x86_64, node 20.19.2, npm 11.21.1; stdio transport

- @modelcontextprotocol/sdk (TypeScript) 1.32.2
- node 20.19.2

**Client used in the test:** Reproduced with the official MCP TypeScript SDK stdio client (StdioClientTransport) 1.32.2 as a stand-in for a desktop app (Claude Desktop, Cursor, etc.), which can't run on the Linux test box. Not tested in the desktop app itself.

## Root cause
stdio clients don't pass their whole environment to servers. The SDK's `getDefaultEnvironment()` passes only a safe list on POSIX (HOME, LOGNAME, PATH, SHELL, TERM, USER; `DEFAULT_INHERITED_ENV_VARS` in `client/stdio.js`). Desktop apps launched from the Dock or Start menu never had your shell variables in the first place.

## Fix steps
1. Declare each variable the server needs under `"env"` in that server's config entry.
2. Restart the client.

## Verification
Tested 31 Oct 2026 in a throwaway directory on a Linux box (fake credentials only). Before (A) and after the fix:

```
A key only in parent env: CALL: "ERROR: DEMO_API_KEY is not set"
B key under "env":        CALL: "DEMO_API_KEY is set (len 19)"
```

## Sources
- https://modelcontextprotocol.io/legacy/tools/debugging