ChatGPT plugin extensions and MCP Events: what to build
ChatGPT plugin extensions add app interfaces; MCP Events starts saved tasks when connected data changes. Learn what to build, how to submit and which limits apply.
A connected service can notify ChatGPT when something changes and start a user-defined task without another prompt. MCP Events provides that trigger; ChatGPT plugin extensions put your app's interface alongside the conversation. OpenAI's DevDay recap
Together, they give ongoing work a more practical home in ChatGPT. OpenAI reports a potential audience of 1.2 billion weekly users, though that isn't a forecast for your plugin. After DevDay on 29 September 2026, your job is to decide which part of the product belongs there and what still needs to run in your own service.
Where ChatGPT plugin extensions put your app
OpenAI's extension guide describes interfaces in the sidebar, beside a conversation or when users open supported files. Extensions also cover settings, deep links, richer forms and sharing context between the model and an app. Users can work with the interface during the task instead of following a link elsewhere. Plugin extensions guide
| Surface | A useful product role |
|---|---|
| Sidebar app | A persistent place to browse and work |
| Conversation panel | A focused interface beside the current discussion |
| File viewer or editor | Product-specific handling of a supported file |
| Composer mention | Selecting a particular item as context |
| Rich form | Collecting structured choices before a tool acts |
Start with the surface that removes your most awkward handoff. You have building blocks here, not an obligation to squeeze the whole app into ChatGPT.
For an asset library, browsing may beat another text response. For a file product, an editor may matter more than a sidebar home. For a workflow app, selecting the exact record can matter more than either. Let the repeated job decide which interface you build.
Canva, Figma and Adobe picked different surfaces
Canva uses a sidebar feature for creating and previewing designs. Figma provides composer mentions for finding and referencing files in the desktop app. Adobe uses file handlers for editing with Acrobat and Photoshop inside ChatGPT. OpenAI's extension examples
Each connects a familiar action to the place in ChatGPT where it makes sense. A document editor benefits from opening the document; a design service benefits from showing the design. You don't need to copy the same surface as every launch partner.
Composer mentions are desktop-only. The extension guide also says web extensions for Free and Go are coming soon, narrowing the recap's broader all-plans wording. Existing plugin functionality is unaffected.
If onboarding depends on a mention picker, test on desktop first. If your users mainly work on the web, confirm the required extension is available to their actual plan before making it the main route into your product.
Plugin Creator helps; review still comes before publishing
Plugin Creator helps prepare plugins and submission materials. Install it from the directory, start a conversation with @plugin-creator and specify a workflow, according to the help page. A plugin can contain reusable instructions, connected apps or both; creating it doesn't authorize every user's connected accounts. Plugins in ChatGPT help
For public distribution, the submission guide separates the ZIP package from the connected MCP server and its scanned tools. Upload the package, review automated findings, complete the review information, submit the selected draft and publish after approval. Plugin submission guide
You must resolve required setup and validation errors. Other automated findings can go to the review team for consideration. Human review doesn't let you bypass required checks or guarantee that every rejection can be resolved without another upload.
For MCP integrations, the guide asks for five positive test cases, three negative cases, a video walkthrough and release notes. Provide a dedicated test account when sign-in is needed, and put reviewer credentials in review details, outside the public package.
Write the negative cases early. If your product can't explain when it should decline an action, a richer interface won't fix the ambiguity.
Discovery can happen in the conversation
OpenAI's redesigned discovery includes ranking and recommendations in the directory and in conversations. Users still choose plugins and approve their access: a recommendation doesn't install a plugin or connect an account. DevDay recap
Installed tools can be selected explicitly with an @ mention or used for a relevant task, according to the plugin guide. Desktop-only plugins stay restricted to that surface, even when users discover them elsewhere. ChatGPT plugin guide
Write your listing around the task someone can complete, the information it needs and the result they should expect. A list of generic AI capabilities doesn't help much when you're deciding whether to connect an account.
An r/mcp post about mapping app descriptions makes a related point: directory supply doesn't establish repeat usage or developer revenue. That's the author's observation about their directory analysis, rather than an official measure of plugin success. The discussion
Measure your own completed workflows and repeat use. OpenAI's audience figure tells you where distribution might happen, but it can't tell you how many people want the specific thing you're building.
MCP Events starts work when a change arrives
MCP Events lets ChatGPT subscribe to updates from an MCP server. The user chooses what to watch and what should happen. Your server advertises events, receives a subscription with a callback destination and sends matching updates; ChatGPT follows the saved instructions when they arrive. MCP Events developer guide
The guide gives examples such as responding to a new message or a document comment. You could design a review workflow that monitors one document, reads a new comment and prepares a proposed revision for its owner. That's an illustrative design, rather than a feature every document plugin ships.
A scheduled job periodically asks whether work exists. An event reports that a specific change occurred. That's the difference to weigh when deciding how the next step should start.
Keep the event narrow. A notification should identify the changed record and let a read tool fetch more detail. It shouldn't quietly expand a drafting task into permission to publish the result.
The draft protocol has explicit delivery limits
ChatGPT's integration requires MCP 2.0, with protocol version 2026-07-28. It supports webhook delivery and callback verification from the draft MCP Events specification; polling, streaming and the draft's gap and termination control notifications are unsupported here. This is partial support for a draft, not a final, universally supported MCP standard. Protocol support details
Your server needs persistent subscriptions and outbound HTTPS. It implements events/list, events/subscribe and events/unsubscribe. Deliveries are signed, and a successful receipt is processed asynchronously.
Repeated or out-of-order delivery is possible, so write tools should avoid duplicating changes. Test beyond the happy path:
- Repeating an event should not create a second copy of the same output.
- Revoking access should stop delivery of protected information.
- Restarting the server should not silently lose its subscriptions.
- An app update caused by the task should not create an endless feedback loop.
These tests follow from the integration's behavior. Give them particular attention when the response can change data instead of merely summarizing it.
Build one repeatable task before adding its trigger
Choose a task people already repeat in your product. Add the minimum interface needed to inspect the work, then decide whether an event improves its timing. Start small enough that you can check the whole task.
A comment review tool could begin with a side panel showing the source comment and proposed response. Have the user request the review in the first version. Once that path works, an event can start the same bounded task when a new comment appears.
Check whether the user can identify the source and correct the result. Does the action use the intended account? Does stopping the monitor stop future work?
A useful plugin earns its place by making a repeated job easier to complete and check. More surfaces and triggers help when they improve that job; they don't answer the product question for you.
FAQ
What are ChatGPT plugin extensions?
They add app interfaces to supported ChatGPT surfaces, including sidebar apps, conversation panels, file viewers and forms.
Is Plugin Creator required to build a plugin?
No. It helps with creation and submission preparation; developers can also build and package an integration using the published guides.
Is MCP Events a finished standard?
No. OpenAI supports part of the draft specification, with webhook delivery and explicit exclusions.
Can an event run without a new user prompt?
Yes, once the user defines what to monitor and how to respond. Required account access and action permissions still apply.