MCP troubleshooting
Most Cmdop MCP failures are one of three things: the assistant is not registered
with Cmdop, the assistant is registered but the target machine is offline or
needs a connection step, or an external MCP server has not been reviewed and
approved yet. Start with cmdop mcp status and cmdop mcp tools. Find your
symptom below.
My assistant cannot see my machines
cmdop mcp status
cmdop mcp toolscmdop mcp statusshows which local assistants Cmdop is registered with. If yours is missing, runcmdop mcp install --agent claude(or--agent codex).- The registration points at a specific
cmdopexecutable. If you moved or reinstalled the binary, register again. - The machine must have joined a relay. Run
cmdop status; if it is not connected, fix that first — see Joining and access issues. - Start a fresh assistant session after registering. Claude Code may need its plugin reload action instead.
cmdop mcp tools lists what your installed version actually offers. If a tool
you expect is absent there, the assistant will not have it either.
My assistant sees the machines but a call fails
Registration is not reachability. The target machine still has to be online, and
it can still require a connection step. Check the target with cmdop status on
that machine, or ask Cmdop to list machines and look at their presence.
A Cmdop agent cannot call an external tool
cmdop mcp servers listWork down this list:
| What you see | What to do |
|---|---|
| The server is not listed | It was discovered, not installed. Import it explicitly, or add it with cmdop mcp servers add. |
| Listed but off | Complete the review, test, and approve steps. See External MCP tools. |
| Enabled but stopped | Normal. The process starts on the first real tool call. |
| Needs attention | The server’s tool list changed, so the old approval was withdrawn. Review the added, changed, and removed groups and approve the replacement. |
| Review shows no change groups | This is a first inspection, not “nothing changed”. Read the whole tool list. |
| The manager is unavailable | Run cmdop status and restart the agent on that machine rather than editing configuration files by hand. |
| A call failed | Approval covers one exact tool catalogue. If the server was edited, test again and approve the new candidate. |
An MCP server is reachable from a browser
Treat an HTTP-based MCP server as a network service, even when it is bound to
localhost. Recent MCP SDK advisories have centered on DNS rebinding against
local HTTP servers, where a malicious website can try to reach a server that the
user thought was private to their machine. Start by updating the MCP server SDK,
then confirm its host, origin, and authentication settings before approving it
inside Cmdop.
Cmdop’s approval flow does not make an unsafe external server safe. It gives a Cmdop agent permission to call the exact tool catalogue you reviewed. If that server also listens for browser or network traffic, secure that server as its own surface before approving it.
Use this rule of thumb:
| Server shape | What to check before approval |
|---|---|
| Stdio server started by Cmdop | Review the command, environment, and tool catalogue. |
| Local HTTP/SSE server | Check SDK version, host/origin protections, authentication, and whether a browser can reach it. |
| Remote MCP server | Treat it like any other internet service: authentication, TLS, ownership, and logs matter. |
For background on the MCP Python SDK DNS rebinding advisory, see GHSA-9h52-p55h-vw2f .
States that look alike but are not
A Marketplace listing, a definition found in another client’s configuration, and an approved server that happens to be stopped are three different things. None of them means a tool is ready to call. Only an enabled, approved Cmdop-owned server does.
Common questions
Why can my MCP assistant not see Cmdop machines?
Usually the assistant is not registered with Cmdop, the registration points at
an old binary, or the machine has not joined a relay. Start with
cmdop mcp status, cmdop mcp tools, and cmdop status.
Why does an MCP tool call fail after machines are visible?
Machine visibility is not the same as reachability or permission. The target machine still has to be online and may require a connection step.
Should I approve an external MCP server just because Cmdop discovered it?
No. Review, test, and approve the exact tool catalogue first. If the server changes later, review the changed catalogue again.
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