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The Nuntly MCP server (@nuntly/sdk-mcp) gives Claude Code tools to send email, manage domains and webhooks, and read and reply to inbound messages. Check the prerequisites first: an API key and Node.js 20 or later.

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Set up from a one-line prompt

Paste this line into Claude Code, in the project you want to set up. The agent follows an install guide written for it, asks you to create the API key, sends a test email to your address, and ends with a setup report.
To set it up yourself, follow the steps below.

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Create an API key

In the dashboard, go to API Keys and create a key with the Sending only permission, and leave Restrict to domains empty. Copy it. Pick Full access instead for an agent that manages domains, inboxes, webhooks or agent memory. See API keys.

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Add the MCP server

Exit Claude Code if it runs, then run this from your project root, since Claude Code registers the server for the directory you run it in. Paste your key when the cursor waits, and press Enter. In PowerShell, keep '--' in quotes so that an npm-installed claude.ps1 passes it on:
The key never shows on screen (PowerShell shows * for each character) and never lands in your shell history. Claude Code stores the server in ~/.claude.json (%USERPROFILE%\.claude.json on Windows), scoped to this project. Start a new Claude Code session, then check the connection:
The nuntly line reads Connected.

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Share the server with your team

Commit a .mcp.json file at the project root. It reads the key from the environment Claude Code starts in, so each person sets their own NUNTLY_API_KEY. Claude Code asks each person to approve a project server on first use. When the variable is unset, it passes the literal ${NUNTLY_API_KEY} text, which makes every call fail with a 401:
.mcp.json

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Send a test email

Ask your agent: “Send a test email from hello@onboarding.nuntly.com to my address.” Use the email address of your Nuntly account (the organization owner), exactly as you signed up. This sender only delivers to that address.

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Troubleshooting

Claude Code shows Failed to connect for nuntly. The first download can outlast the health check, so wait a few seconds and run claude mcp list again. If it still fails on native Windows, run claude mcp remove nuntly, then add the server again with cmd /c npx -y @nuntly/sdk-mcp@2 in place of npx -y @nuntly/sdk-mcp@2. Claude Code shows your key. claude mcp get nuntly prints the server’s environment, key included. Use claude mcp list to check the connection. For errors shared by every client, such as a tool that returns isError: true, see Troubleshooting.

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Next steps

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