Troubleshooting and FAQ

Common issues, questions, and solutions for the Nium MCP Server.

Troubleshooting

Common issues

Symptom	Fix
Nium tools don't appear in my client	Restart the client fully after saving the config. For Claude Desktop, quit the app entirely — a window close isn't enough.
401 Unauthorized	Check that NIUM_API_KEY in your config matches the key from Nium Portal. Keys are environment-specific — make sure you're using a Sandbox key.
url entry ignored in Claude Desktop	Claude Desktop doesn't support native remote HTTP. Switch to the mcp-remote config shown in the Claude Desktop tab of the install guide.
Gemini CLI can't connect	Check you're using httpUrl, not url. The url field routes to an SSE server.
Codex tools not loading	Confirm the top-level key is mcp_servers (snake_case). mcpServers is not valid TOML for Codex.
url works in Cursor but key is missing	Confirm env contains NIUM_API_KEY and headers references it as ${env:NIUM_API_KEY}.

Still stuck?

Open an issue on GitHub or email developers@nium.com.

FAQ

Is it free?

Yes. The MCP Server usage is free.

Can it access my production account?

No. It runs against Sandbox only and cannot read or modify production data.

Will it take Sandbox actions without me asking?

No. Every Sandbox action requires an explicit instruction from you.

Which languages does it generate code in?

Any language. Node.js, TypeScript, Python, Go, and curl produce the most reliable output.

How do I switch between Sandbox and Production once production is available?

You'll use a different API key and server URL. The config structure stays the same. Email developers@nium.com to register interest in production support.

What if I'm behind a corporate firewall or managed network?

Ask your IT team to allowlist mcp-sandbox.nium.com on port 443.