How to Add an MCP Server to Claude Code, Step by Step

This guide is for people who build with Claude Code in the desktop app or a browser and want to connect a tool to it for the first time. It shows you how to add an MCP server to Claude Code, sign in to it, check it's working and fix the common snags.

An MCP server is a small online service that lets Claude Code use another tool, like your email service, database or payments account. MCP stands for Model Context Protocol, an open standard for connecting AI tools to other services (what MCP is, in plain English). In Claude, a connected MCP server is called a connector.

You won't write any code or edit any files. Everything happens in on-screen settings and in the chat. We use SimpleSends, our transactional email service, as the worked example, but the steps are the same for any service that gives you an MCP server URL.

What do you need before you start?

You need four things: a Claude plan that includes Claude Code, the desktop app or a browser, the service's MCP server URL, and an account with that service.

On Team and Enterprise plans, only an Owner (and on Enterprise, some admin roles) can add a custom connector. If that isn't you, send your Owner the URL and ask them to add it. Once they do, it appears in your connector list with a "Custom" label, and you select Connect next to it.

A few services use an API key (a password-like code that identifies your account) instead of a sign-in page. Their setup instructions will tell you if so.

How do you add an MCP server to Claude Code?

You add it once, under Customize, then Connectors, and Claude Code picks it up from your Claude account. Connectors you add there are available in Claude Code sessions in the desktop app and in your browser, as long as you're signed in with the same account.

1. Open Customize. In the desktop app, it's in the sidebar. In a browser, sign in at claude.ai and open Customize.
2. Open Connectors.
3. Choose Add, then Add custom connector.
4. Enter a name (this is what you'll see in your connector list) and the MCP server URL.
5. If you see a Continue button, select it. Claude checks the URL and fills in the sign-in settings it detects. Leave those as they are unless the service's instructions say otherwise.
6. Select Add.

If the service is listed in Claude's Connectors Directory, you can pick it from the directory instead of typing a URL. A custom connector is for services that aren't listed, or that give you their own URL.

You can also reach your connectors from inside a Claude Code session in the desktop app. Select the + button next to the message box, then Connectors. From there you can switch connectors on or off, or choose Manage connectors.

Worked example: connecting SimpleSends to Claude Code

Here's the same process with SimpleSends, a transactional email service built for people who build with Claude Code but don't write code. Transactional emails are the automatic messages your project sends to one person at a time, like a welcome email or a password reset.

1. Sign up on the SimpleSends website and follow the steps there to set up the email address you'll send from. To send from your own domain, this includes adding a few DNS records where your domain is registered. (DNS records are short settings that tell the internet which services can send email for your domain.) You can't sign up inside the Claude Code chat.
2. In Claude Code, open Customize, then Connectors, choose Add, then Add custom connector. Fill in these two fields:

3. When Claude prompts you to connect, log in to SimpleSends.
4. Back in the Claude Code chat, tell Claude Code you've connected it:

I've connected SimpleSends for all transactional email.

Claude Code takes it from there, including adding what your project needs to send email. If you're wondering what an email connector actually does while you build, see what an email MCP server is. For the full journey from here, read how to send emails from Claude Code.

What happens when Claude prompts you to log in?

Claude opens the service's own sign-in page. You log in there and approve access, and Claude gets permission to use the service on your behalf without ever seeing your password.

A few things are worth a moment's attention:

• Check the account. If you have more than one login for the service (work and personal, say), make sure you sign in to the one your project uses.
• Read what access it asks for. The sign-in page lists what Claude will be allowed to do. If it asks for more than the job seems to need, you can decline.
• Watch the first few approvals. The first time Claude Code uses one of the connector's tools, you may see an approval request. Approve it once while you get to know the connector. Only choose to always allow a tool when you trust the service to act without you checking each step.

Only connect services from companies you trust, because a connector can read and change data in the service it connects to. If you're not sure which ones are worth adding, see the MCP servers worth connecting to Claude Code.

How do you check it's connected?

Look for it in your connector list, then ask Claude Code to use it for something small.

1. In Customize, then Connectors, find the new connector. If it still shows a Connect button, it isn't signed in yet. Select it.
2. In a desktop app session, select + next to the message box, then Connectors, and make sure the new connector is switched on.
3. Ask Claude Code what it can see:

Which connectors can you use in this session? Is SimpleSends one of them?

You should get a list that includes your new connector.

4. Ask for a small, safe task that uses it. With SimpleSends, that's a test email to yourself:

Using SimpleSends, send a test email to hello@yourcompany.com saying the connection works. Then check the recent sends and tell me whether it went out.

Claude Code sends the test, reports whether it was delivered, and the email lands in your inbox. Test emails like this come from the chat; once your project is live, real emails go out from the project itself. There's more on this in testing your emails before your users see them.

In cloud sessions, the + button isn't there. Those sessions use the connectors from your Claude account automatically.

What if the connector isn't working?

Most problems come down to the account you're signed in with, the URL, or a sign-in that needs redoing.

If none of these fix it, the service's own help docs are the next stop, since the MCP server belongs to them. And if you're still finding your feet with Claude Code in general, our beginner's guide to Claude Code covers the basics.