How to add a custom MCP server to ChatGPT
The current steps to add a remote MCP server to ChatGPT as a custom plugin, sign in with OAuth, and fix tools that don't show up.
Updated
Short answer
On ChatGPT's website, open Plugins, click Add (+) and choose Create custom MCP server. Give it a name, paste the server's address, pick the sign-in type, accept the warning and click Create as a plugin. It takes about two minutes. You no longer turn on developer mode first: OpenAI removed that switch on October 1, 2026.
An MCP server is a connector that lets ChatGPT use another app. This guide works for any remote MCP server, with Upsy as the example.
What changed: developer mode is gone
Can't find Developer mode? In an October 1, 2026 forum post, OpenAI's plugins team said:
- Eligible users can add custom MCP servers without turning on developer mode.
- The Create MCP App button became Create custom MCP server.
- The Enforce CSP for custom apps setting moved to Settings › Security and login.
- In work workspaces, the admin permission called Developer mode is now Create custom MCP servers, with the same settings as before.
OpenAI's developer docs describe the new flow, and call the button Add custom MCP server; you may see either label. Some help-center pages still describe the old toggle.
What you need
- ChatGPT on the web. You add the server at chatgpt.com/plugins, not in the phone app.
- A remote server. ChatGPT connects over the internet to an HTTPS address that speaks Streamable HTTP or SSE. For a server on your own computer or private network, OpenAI offers a Secure MCP Tunnel instead.
- A sign-in type. ChatGPT supports OAuth, no authentication, or a mix of the two. With OAuth it registers itself (dynamic client registration or a Client ID Metadata Document) when the server supports it, so most servers need no client ID or secret.
- Your plan. OpenAI's developer docs don't list a plan limit, and OpenAI said "all eligible users" can now add one. Older help pages describe write actions as a Business and Enterprise feature, so if the option is missing on a personal plan, check your plan first.
- In a work workspace, an admin. The admin has to allow custom MCP servers for your role (Create custom MCP servers, shown in some workspaces as Create plugins with MCPs). On Enterprise it's off by default.
Add a custom MCP server (Upsy as the example)
For Upsy, first sign up free at upsy.ai and connect your apps on the Apps page. Then open Assistants, click Add assistant and pick ChatGPT.
In ChatGPT on the web, open Plugins in the sidebar.
Click Add (+), then Create custom MCP server.
Enter a name and an optional description. For Upsy, name it Upsy.
Under Connection, paste the server's URL. For Upsy:
https://upsy.ai/connectOther servers often end in
/mcp. Use the exact address the service gives you.Set authentication. For Upsy, choose OAuth and leave any client ID and secret fields empty.
Read the risk warning and select I understand and want to continue.
Click Create as a plugin. ChatGPT reads the server's tools and shows them.
Click Connect if ChatGPT asks. A sign-in page from the server opens. On Upsy's page, sign in, choose what ChatGPT can use for each app, and click Allow.
Install the new plugin if ChatGPT shows Install plugin. It's listed under your personal plugins.
Check that it works
Start a new chat, type @, pick your plugin and ask for something small. For Upsy:
@Upsy What can you do with my connected apps?
ChatGPT should call Upsy's upsy_connectors tool and list each app and account with its access, such as "Gmail (you@gmail.com): Read-only". In Upsy, ChatGPT now appears on the Assistants page.
How ChatGPT asks before using a tool
- ChatGPT reads each tool's
readOnlyHint. Tools marked read-only can run without asking. Every other tool counts as a write action, and by default ChatGPT asks you to confirm it. - You can tell ChatGPT to remember your approve or deny choice for one tool for the rest of a chat. A new chat asks again.
- Settings › Plugins › Permissions sets your default: Always ask, Allow read actions, Allow low-risk actions or Allow all actions. See Managing app permissions in ChatGPT.
Upsy marks every read tool as read-only, and marks sending, deleting and browser clicks as sensitive. Upsy has no approval prompt of its own, so ChatGPT's prompt is your last check before a send.
Keep the tool list up to date
ChatGPT saves the server's tool list when you create it. The plugin's settings page lets you turn single tools on or off, and Refresh pulls the server's latest tools and descriptions. Refresh after the server changes, then start a new chat.
With Upsy, you can connect a new app mid-chat and ChatGPT still reaches it through Upsy's app_tools tool. Refreshing makes its own tools show up directly.
Troubleshooting
Developer mode is missing
You don't need it any more. Go to Plugins, click Add (+) and look for Create custom MCP server or Add custom MCP server.
Create custom MCP server doesn't show
In a work workspace, your admin hasn't allowed custom MCP servers for your role. Ask them to turn on Create custom MCP servers in workspace settings under Permissions & roles. On a personal account, check that you're on chatgpt.com in a browser and that your plan includes it. In early October, some Business and Pro workspace owners reported the error "You need workspace admin permission to create a draft app" even as admins. If that's you, contact OpenAI support.
ChatGPT can't connect to the server
Check the address character by character, including the path. The server must be reachable over public HTTPS: localhost addresses don't work without a Secure MCP Tunnel. For Upsy, the address is https://upsy.ai/connect, not /mcp.
I only see some of Upsy's tools
You probably installed Upsy from its listing in ChatGPT's plugin directory. That listing's tools were fixed when it was submitted, before any apps were connected, so it has memory, files and the browser but not Gmail, Calendar or Slack. Reinstalling it doesn't help. Remove it and add Upsy as a custom MCP server with the steps above. If you added it that way and a tool is still missing, check that ChatGPT's access to that app isn't No access on its page in Upsy, then click Refresh.
The sign-in page names Codex, not ChatGPT
ChatGPT may sign in to a server as Codex, OpenAI's coding app. On Upsy's page, check the line under the heading: if it redirects to chatgpt.com, it's your ChatGPT.
ChatGPT asks me to sign in again
ChatGPT keeps access with a refresh token. If a server doesn't offer one, ChatGPT loses access when the first sign-in expires. Open the plugin under Settings › Plugins and select Reconnect or Connect.
Tools stopped working in our workspace
A workspace uses the snapshot of tools its admin approved. If the server changes a tool, calls can fail until an admin refreshes the tool list in workspace settings.
Security and privacy
OpenAI labels custom MCP servers as elevated risk and doesn't review them. A server you add can see what ChatGPT sends it, and a bad one could steer ChatGPT into changing or deleting data. Only add servers from people you trust, and read the tool list ChatGPT shows before you connect.
With Upsy, ChatGPT never gets your app passwords or tokens: it calls Upsy's tools, and Upsy calls the app. You choose ChatGPT's access per app (Full access, Read-only, Pick actions or No access), every action is in Upsy's History, and Upsy emails you when one assistant sends 20 or more messages, deletes 50 or more items, or reads from your apps 100 or more times within 10 minutes. One click on the assistant's page turns ChatGPT off. More in is it safe to connect Gmail to ChatGPT?.
FAQ
Is ChatGPT developer mode gone?
Yes, for adding custom MCP servers. Since October 1, 2026 you add one from Plugins without a separate switch, and the admin permission is now called Create custom MCP servers.
How do I create an MCP app in ChatGPT?
The old Create MCP App button is now Create custom MCP server, under Plugins › Add. ChatGPT creates the server as a plugin you can install and mention with @.
Can I add a custom MCP server on the ChatGPT phone app?
Not when you're setting it up. Add it on chatgpt.com in a browser.
Can ChatGPT connect to a local MCP server?
Not directly. ChatGPT only reaches servers on the internet. Use OpenAI's Secure MCP Tunnel, or host the server at a public HTTPS address.
What's the difference between a ChatGPT custom connector and a plugin?
They're the same thing under newer names. A custom connector became a custom MCP app, and ChatGPT now creates it as a plugin. See the ChatGPT connectors hub for how apps and plugins fit together.
Related guides
- How to connect multiple Gmail accounts to ChatGPTChatGPT now connects more than one Gmail account. How to add a second inbox, and how to give each one its own access in ChatGPT and your other assistants.
- How to connect a personal Outlook account to ChatGPTChatGPT's Outlook connector only takes work and school accounts. How to let ChatGPT read and send from a personal Outlook.com or Hotmail account.
- How to share memory between ChatGPT, Claude and GrokStop repeating yourself. Move your memory from ChatGPT to Claude, or keep one memory that ChatGPT, Claude, Grok and Muse all read and you control.
- Is it safe to connect Gmail to ChatGPT?What ChatGPT can see and do once Gmail is connected, the real risks, and how to give it read-only access, review what it did and turn it off fast.
- Can ChatGPT book flights and hotels for you?What ChatGPT's travel apps and cloud browser can and can't book, where they stop at logins and payments, and how to use a browser signed in to your sites.
- Can ChatGPT fill out forms for you?How to get ChatGPT to fill out online forms and applications with your own details, in a browser signed in to your sites, while you watch and approve.