MCP server can't find a program it needs
Some MCP servers wrap another command-line program. If that program isn't installed, or isn't on the PATH the client gives the server, the server exits at start. We recorded this for lbrain agent memory and gcloud MCP (Google Cloud).
Install the program the message names, check it with command -v <name>, and if your client still can't find it, use its full path or add its folder to PATH in the server's env block.
Last tested 2026-11-11
How we test: methodology. Context cost: lowest context cost MCP servers. Not tested by us: security, output quality, and behaviour with real credentials.
Symptom
The server exits at once. Its stderr says a program is "not on PATH" or that an executable was "not found".
The exact errors we saw
| Server | What it printed (verbatim) | Where we saw it | Tested |
|---|---|---|---|
lbrain agent memorylbrain-coding-agents 0.1.3 | lbrain is not on PATH. Install the engine first: | stderr at launch (exited code 1) | 2026-11-10 |
gcloud MCP (Google Cloud) (not listed on TestedMCP)@google-cloud/gcloud-mcp 0.5.3 | ERROR: Unable to start gcloud mcp server: Error: gcloud executable not found | stderr at launch (exited code 1) | 2026-11-11 |
Cause
The MCP server is a thin layer over another program: the lbrain engine for lbrain agent memory (its next line names pip install "lbrain[local]"), and the Google Cloud CLI for the gcloud MCP server (not listed on TestedMCP). Our sandbox had neither one installed.
Fix
- Install the program the message names, for example the gcloud CLI (Google Cloud CLI install). not tested by us
- Check it from a terminal:
command -v gcloudshould print a path. not tested by us - Installed, but the client still can't find it? An app started from a desktop launcher can get a shorter PATH than your terminal. Use the program's full path, or set
PATHin the server'senvblock. not tested by us - If
npxoruvxitself is missing: we did not record this case, but the same PATH check applies. npx comes with Node.js and npm (Node.js download, npx), and uvx comes with uv (uv installation, uvx).
Affected listings
- lbrain agent memory (
lbrain-coding-agents, tested 2026-11-10, status failed)
More troubleshooting: all troubleshooting pages · MCP error -32000: Connection closed · MCP servers that need an API key or sign-in. Quotes are verbatim from our own test logs (colour codes removed; a trailing … marks a shortened line). We have not run these servers inside Claude Code, Claude Desktop or Cursor.
FAQ
What does 'executable not found' mean for an MCP server?
The server tried to start another program it depends on, such as the gcloud CLI, and could not find it on the PATH it was given.
Why does it work in my terminal but not in my MCP client?
The client starts the server with its own environment. An app started from a desktop launcher can have a shorter PATH than your shell. Using the program's full path avoids the difference.