An MCP server is the piece a service publishes so an AI assistant can use that service for you: it lists what the assistant may do (look up an invoice, create a task, make a QR code) and does it only after you sign in and press Allow.
You do not need to know how it works to use one, the same way you do not need to know how a card reader works to pay. This post explains the idea in plain words, what changes for you once a server is connected, what it can and cannot see, and how to tell a good one from a bad one.
What does MCP stand for, and why does it exist?#
MCP stands for Model Context Protocol, a shared standard for connecting AI assistants to other software, published as an open specification in late 2024 and now supported by Claude, ChatGPT, Cursor, Claude Code and many other tools.
Before it, every assistant needed its own custom integration with every service, so most services had none. With one standard, a service builds one server and every assistant that speaks the standard can use it. That is why the same QR code connector works in Claude and in ChatGPT with the same address.
What is an MCP server, and what does it actually do?#
An MCP server does three things: it tells the assistant which tools it offers, it describes each tool in words the assistant can read, and it runs a tool when the assistant asks, inside your account.
A tool is one action with a name and a short description. A QR code server, for example, offers tools such as "create a QR code", "change where a code points", "get scan statistics" and "list my link domains". When you type "make a QR code for our menu", the assistant reads those descriptions, picks "create a QR code", fills in the address and the label from your sentence, and calls it. The server does the work and sends back the result, and the assistant shows it to you.
Nothing is guessed on the server's side. If a tool needs a plan you do not have, the server says so in words, and the assistant passes that on instead of inventing a result.
What changes for you once a server is connected?#
Once a server is connected, the assistant can do things in that service instead of only talking about them.
| Without a server | With a server |
|---|---|
| "Here is how to make a QR code" | The code is made, in your account, with a link |
| "You could check your invoices" | "Three invoices are unpaid, totaling $940" |
| A picture of a QR code that cannot change | A code you can re-point later without reprinting |
| Copy the answer, open the tool, do it yourself | Ask, approve, done |
The assistant also becomes honest about limits. A connected server tells it what your plan allows, so "make me a code I can change later" on a free plan gets a clear "that needs Premium" instead of a confident wrong answer.
What can an MCP server see, and what can it not see?#
An MCP server sees only what you allowed on its sign-in page, inside that one service, and nothing about your other chats or other tools.
The sign-in is the whole story. When you connect, the vendor's own page opens (a Google page for Google, a QRFLOW page for QRFLOW), lists the permissions in plain words, and asks you to allow them. The assistant never sees your password. From then on:
- The server sees requests the assistant makes on your behalf, and the data needed to answer them.
- The server does not see your conversation, your other connectors, or your files elsewhere.
- Actions that cannot be undone are marked as such, so a well-built assistant asks before, for example, deleting something.
- You can revoke access from the assistant's settings or from the vendor's account page at any time.
The Claude connectors post walks through what to check on that page before you press Allow.
How do you add an MCP server?#
You add an MCP server by pasting its address into the assistant's settings, signing in on the vendor's page and pressing Allow; the whole thing takes about a minute.
- Find the server's address on the vendor's site. It usually ends in /mcp; QRFLOW's is below.
- In Claude: Customize, then Connectors, then Add custom connector. In ChatGPT: turn on Developer mode, then Settings, Plugins, and the plus button.
- Paste the address and give it a name.
- Sign in on the page that opens and press Allow.
- In a new chat, turn the server on from the tools menu and ask in plain words.
https://qrflow.codes/mcp
Servers listed in the assistant's own directory skip step one: press Connect and sign in. The assistants page has the exact clicks for Claude, ChatGPT, Cursor and Claude Code, with drawings of each screen.
How do you tell a good MCP server from a bad one?#
A good MCP server runs on the vendor's own domain, signs you in on the vendor's own page, and describes each tool plainly.
- Own domain. A QR code server should live on the QR code company's site, not on a stranger's. The address tells you.
- Proper sign-in. A page that lists permissions and has an Allow button. A server that asks you to paste a password or an API key into the chat is a red flag.
- Plain tool descriptions. You can read what each tool does in the assistant's tool list. Descriptions that tell the assistant how to behave, rather than what the tool does, are a sign of trouble.
- Reversible by default. Pausing before deleting, confirming before anything permanent.
- A published policy. A privacy page that says what the server records and for how long.
Directories such as the ones inside Claude and ChatGPT check these before listing a server, which is a reasonable reason to start there.
Questions people ask#
Is an MCP server the same as a plugin or a connector?#
Yes, seen from three sides. The vendor runs an MCP server; Claude shows it as a connector; ChatGPT shows it as a plugin or app. Same standard, same sign-in.
Do I need to install anything?#
Not for a remote server, which is what most services offer: it is an address you paste. Local servers run on your own computer and are meant for developers.
Can one assistant use several servers at once?#
Yes. "Make a QR code for the new page and post it in the team channel" can use a QR server and a chat server in one request, if both are connected.
Is it safe?#
As safe as the permissions you grant on the sign-in page, which is the same trust you place in any app you connect to your accounts. Read the list, allow only what you would want an assistant to do, and disconnect anything you stop using.
What does QRFLOW's MCP server do?#
QRFLOW's MCP server lets Claude, ChatGPT, Cursor or Claude Code make QR codes of any kind, change where a printed code points, name its link on your domain, pause or expire it, make many at once, and read scan numbers, all inside your own QRFLOW account. The Claude and ChatGPT pages show the setup.
If you would rather skip the assistant, the free QR code generator makes a code in ten seconds with no account.