> ## Documentation Index
> Fetch the complete documentation index at: https://nuntly.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshoot the MCP server

> Fix a Nuntly MCP server that does not appear or start in your client, and read the 401 and 403 errors a tool returns when a call fails.

These errors apply to every MCP client. For an error specific to your client, see its page: [Claude Code](https://nuntly.com/docs/guides/ai-agents-claude-code.md#troubleshooting), [Cursor](https://nuntly.com/docs/guides/ai-agents-cursor.md#troubleshooting), [VS Code](https://nuntly.com/docs/guides/ai-agents-vscode.md#troubleshooting), [Codex](https://nuntly.com/docs/guides/ai-agents-codex.md#troubleshooting) or [Gemini CLI](https://nuntly.com/docs/guides/ai-agents-gemini-cli.md#troubleshooting).

## The server does not appear in your client

Check the JSON syntax of the configuration file: a trailing comma breaks the whole file. Restart the client, and run `npx -y @nuntly/sdk-mcp@2` in a terminal. It prints `NUNTLY_API_KEY environment variable is required.` or waits silently: both mean the command resolves. Press Ctrl+C to stop it.

## `NUNTLY_API_KEY environment variable is required.` at startup

The server reads the key from the `env` of its client configuration. Put it there.

## `command not found: npx` or `The term 'npx' is not recognized`

The first message comes from bash, the second from PowerShell. Install the current LTS release of Node.js from [nodejs.org](https://nodejs.org).

## A tool returns `isError: true`

The result text gives the HTTP status, the error title and the request id. Give the request id to support.

* A `401` titled `Onboarding emails can only be sent to the organization owner` means the recipient is not your account address. Any other `401` means the key is wrong, revoked or mistyped.
* A `403` that names a domain means the key is restricted to other domains: clear **Restrict to domains** on the key.
* A `403` that says the organization is not active means it cannot send: contact support.
* Any other `403` means the key lacks the permission, for example a **Sending only** key on a tool that reads or manages resources.

## A tool rejects an argument

The server refuses an argument the tool does not declare and sends no request. Use the argument names that `tools/list` returns, for example `scheduledAt`.


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