Most businesses should build an MCP server first. A ChatGPT app, which OpenAI now ships as a plugin, is that same MCP server plus written skills and, if you want, your own screens inside ChatGPT. Don’t start a new Custom GPT: OpenAI retires them on Dec 11, 2026.
Who this is for: a business that wants customers or staff to use its product from inside ChatGPT, and is choosing what to pay for. If you only want ChatGPT to read your files in Drive or SharePoint, you don’t need any of the three. Read how to connect company data to ChatGPT instead.
Most pages ranking for “ChatGPT app vs MCP server” were written before OpenAI’s plugin change, or skip the Custom GPT retirement. Every OpenAI fact here was checked on 2026-10-13 against OpenAI’s own docs and help center.
The 53-second version
Transcript (the video has no sound; this is every line on screen)
0:00. ChatGPT app, MCP server, or Custom GPT? OpenAI changed the answer in 2026. Here is the short version.
0:05. 1. MCP server: the connector. One server, many AI apps. Your system (orders, stock, CRM) connects to an MCP server, which holds the tools the AI can call. ChatGPT, Claude, and coding tools all connect to that one server. MCP is an open standard. You build the server once and any MCP client can use it. It has no screen of its own.
0:16. 2. ChatGPT app, now a plugin: skills, an MCP server, and your own screen. A user asks “Where is order 4471?” and ChatGPT shows a card: “Order 4471: shipped. Arrives Thursday. 2 items.” with “Track parcel” and “Change address” buttons. That card is your UI, drawn inside the chat. The plugin holds skills (written instructions), the MCP server (the same tools as before), and an optional UI (cards, buttons, forms). OpenAI now ships ChatGPT apps as plugins. One plugin directory serves ChatGPT and Codex, and OpenAI reviews public listings.
0:27. 3. Custom GPT: retiring on Dec 11, 2026. A Custom GPT’s instructions become a skill in the new plugin. Its knowledge files become reference files. Its actions, the calls to your REST API, do not migrate. You rebuild them as an MCP server. OpenAI’s migration tool moves instructions and files into a plugin. Custom actions do not move. You rebuild them.
0:37. So which one? Pick by what you need. ChatGPT, Claude, and coding tools should all reach your data: MCP server. You want a public listing and your own screens inside ChatGPT: ChatGPT plugin. You already run a Custom GPT: migrate by Dec 11. A Custom GPT is no longer a new option. Start with the MCP server. A plugin reuses it.
0:49. Build the server once. Add screens later. dawloom.com
What each one is, in OpenAI’s words
MCP server
An MCP server is a program that offers a short list of tools, such as “get order status”, over the open Model Context Protocol. Any MCP client can call it: ChatGPT, Claude, Cursor, VS Code, and many more. It has no screen. The AI reads the result and writes the answer. Our MCP servers explainer covers what it should expose.
ChatGPT app, now a plugin
OpenAI folded apps into plugins this year. “Plugins are the packages people discover, install, share, and publish in ChatGPT and Codex.” A plugin can hold skills, “An MCP server that exposes tools and connects to external systems”, or both. “ChatGPT and Codex share one universal plugin directory” (OpenAI, plugin architecture).
The screens are optional: “Custom UI is not required for an MCP server” (same page). When you do add one, “Components run inside an iframe in ChatGPT, communicate with the host through the MCP Apps bridge (JSON-RPC over postMessage)” (OpenAI, ChatGPT UI). OpenAI’s help center draws the line like this: “An app connects ChatGPT to a service, such as Slack. A plugin brings apps and skills together” (plugins in ChatGPT).
So “ChatGPT app vs MCP server” is a false choice. The app is built on the server.
Custom GPT
A Custom GPT is ChatGPT with saved instructions, up to 20 knowledge files of up to 512 MB each, and either apps or actions. “A GPT can use either apps or actions, but not both at the same time” (GPTs in ChatGPT). Actions call your REST API through an OpenAPI schema.
Its status in October 2026:
- “Custom GPTs are scheduled to retire on Dec 11, 2026.” Enterprise workspaces with an approved deferral get until Feb 11, 2027 (retirement FAQ).
- “The transition affects all ChatGPT plans” (same FAQ).
- For Enterprise, OpenAI lists “Oct 26, 2026 (planned): Creation of new custom GPTs ends” (same FAQ).
- “New GPT creation and publishing are not available on personal ChatGPT accounts, including Free, Go, Plus, and Pro” (GPTs in ChatGPT).
- Old chats stay: “Your existing conversations with custom GPTs will remain accessible after retirement.”
What moves when a Custom GPT becomes a plugin
OpenAI ships a “Migrate to plugin” option in My GPTs. Here is what it carries over, from the retirement FAQ:
| Part of the GPT | After migration | Work for you |
|---|---|---|
| Instructions | ”become a skill within the new plugin” | Review and test |
| Knowledge files | ”copied into the plugin’s reference files” | Review and test |
| Connected apps | ”added to the plugin as apps” | Test each one |
| Custom actions (your REST API) | “do not transfer through the migration workflow” | Rebuild, usually as an MCP server |
| Drafts and unpublished edits | Not carried over. “Migration uses the GPT’s latest published version” | Publish first |
The last two rows are where the work is. If your GPT called your own API, that link breaks on retirement day unless you rebuild it. OpenAI says “Rebuilding the connection may require a custom MCP server.”
Decision table: MCP server, ChatGPT app, or Custom GPT
| What you need | MCP server | ChatGPT plugin (app) | Custom GPT |
|---|---|---|---|
| Works in Claude, Cursor, VS Code too | Yes | The MCP server inside it does. The skills and listing are ChatGPT and Codex only | No |
| Your own cards, buttons, or forms in the chat | Plain text and data, unless you add MCP Apps UI | Yes, through MCP Apps UI | No |
| A public listing people can find | Not in ChatGPT on its own | Yes, in the plugin directory after review | GPT Store, until retirement |
| Write actions (book, refund, update) | Yes | Yes | Through actions, until retirement |
| Code to write | A small server | The server, plus skills and optional UI | None, or an OpenAPI file |
| Status in late 2026 | Open standard, current spec 2026-07-28 | OpenAI’s main path | Retiring Dec 11, 2026 |
| Pick it when | You want one connector for every AI app, or it’s for your own staff | Customers should find you in ChatGPT and you want a branded screen | You already run one. Migrate it |
Same server, more than one assistant
The reason to start with the server is reuse. Claude supports “Custom connectors using remote MCP” on “Free, Pro, Max, Team, and Enterprise plans. Free users are limited to one custom connector” (Anthropic). Even the screens can travel. The MCP Apps extension lets you “Build interactive UIs for MCP tools … that render inline in Claude, ChatGPT and any other compliant chat client” (MCP Apps on GitHub), and OpenAI says “ChatGPT implements the open MCP Apps standard for UI returned by an MCP server.”
A Custom GPT never left ChatGPT. A plugin’s skills and listing stay with OpenAI. The MCP server is the part you keep whichever assistant your customers use next year.
Who can use what in ChatGPT
| Plan | Add your own MCP server | Full MCP with write actions | Create new Custom GPTs |
|---|---|---|---|
| Free, Go, Plus | Not listed by OpenAI | No | No |
| Pro | Read and fetch only, in developer mode | No | No |
| Business | Yes, admins and owners turn it on | Yes, in beta | Until retirement, where the workspace allows it |
| Enterprise, Edu | Yes, admins grant it by role | Yes, in beta | Ends Oct 26, 2026 (planned) |
Sources: developer mode and MCP apps (“Pro users can connect MCPs with read/fetch permissions in developer mode”; “Full MCP … is rolling out in beta to ChatGPT Business, Enterprise, and Edu plans”), and the GPT pages linked above. Checked 2026-10-13. Developer mode is “web only”.
What a public ChatGPT plugin takes
If you want customers to find you in ChatGPT, OpenAI reviews the plugin first. From the submission guide:
- Organization owners submit, or members with “Apps Management Write”.
- You complete “individual or business verification”.
- You give “Five positive test cases” and “Three negative test cases”, where the plugin should refuse or ask for more.
- “only one MCP server can be connected per plugin.”
- “After initial publication, OpenAI scans your hosted MCP server daily.”
The server behind a plugin also needs a stable public host and, for user data, OAuth 2.1 login. We cover both in where to host an MCP server and how to add OAuth 2.1 to an MCP server.
Selling inside ChatGPT is narrower than the launch posts suggest. External checkout on your own site is “the recommended and generally available approach”, and “current approval is limited to plugins for physical goods purchases.” Checkout in ChatGPT’s own payment sheet is in private beta (OpenAI, monetization).
The audience is large. OpenAI’s DevDay 2026 recap speaks of “our collective 1.2B weekly users”. That number is OpenAI’s own and isn’t independently audited.
FAQ
Is a ChatGPT app the same as an MCP server?
No, but it contains one. A ChatGPT app is now a plugin. The plugin can hold skills, one connected MCP server, and optional UI. The MCP server does the real work and also works in Claude and other MCP clients.
Should I still build a Custom GPT in 2026?
No. OpenAI retires Custom GPTs on Dec 11, 2026, and personal accounts can’t create new ones. Put the instructions in a plugin skill and the API calls in an MCP server.
Can my Custom GPT’s actions be migrated automatically?
No. OpenAI’s migration moves instructions, knowledge files, and connected apps. “GPT custom actions do not transfer through the migration workflow.” You rebuild that connection, usually as a small MCP server in front of the same REST API.
Do I need a UI for my ChatGPT plugin?
Usually not at first. OpenAI says “Custom UI is not required for an MCP server.” Add screens when text isn’t enough, such as a map, a product picker, or a form with many fields.
Can I sell products inside ChatGPT?
Partly. External checkout on your own domain is generally available, but approval covers physical goods only. ChatGPT’s in-chat payment sheet is a private beta for select marketplaces.
We run a public MCP server at https://dawloom.com/mcp, documented on our developer portal, so you can see a small one before you buy one. If you want one for your own product, see MCP servers and AI agents for how we scope and bill the work.