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Heroes of Might and Magic 3Apps SDK
The Apps SDK was OpenAI's 2025 toolkit for building apps inside ChatGPT on the Model Context Protocol (MCP). Since Jul 9, 2026 apps live inside plugins, and the Apps SDK documentation now opens OpenAI's Plugins docs, where you build an MCP server, optional UI and skills and submit them to the ChatGPT Directory.
To build something that runs inside ChatGPT today, you build a plugin: an MCP server that gives ChatGPT live data and tools, optional UI returned from those tools, and skills that wrap them, packaged together and submitted for review to the ChatGPT Directory (OpenAI Plugins docs). That is what the Apps SDK became. OpenAI introduced the Apps SDK in preview in 2025 as "an open standard built on the Model Context Protocol (MCP)" for apps inside ChatGPT (OpenAI); on Jul 9, 2026 the Plugin Directory replaced the App Directory, and the address developers.openai.com/apps-sdk now opens the Plugins documentation. Existing app connections kept working through the change (ChatGPT release notes). For the reader's side of plugins, see Plugins.
Quick facts
| What it was | OpenAI's SDK for apps inside ChatGPT, built on MCP and open source |
| Launched | 2025, in preview; the exact launch day was not confirmed for this page |
| Business, Enterprise, Edu | Apps in preview from Nov 13, 2025 |
| App submissions opened | Dec 18, 2025, with the app directory |
| Became plugins | Jul 9, 2026: Plugin Directory replaced the App Directory |
| Docs today | developers.openai.com/apps-sdk (the Plugins index) |
| A plugin contains | Skills, MCP servers, optional UI |
| Directory | chatgpt.com/plugins |
From apps to plugins: a short history
- 2025: Apps in ChatGPT and the Apps SDK. OpenAI announced apps that users can call in a chat, with "Developers can start building them today with the new Apps SDK, available in preview" (OpenAI). Pilot partners were Booking.com, Canva, Coursera, Figma, Expedia, Spotify and Zillow. Apps first reached logged-in users outside the European Economic Area, Switzerland and the UK on the Free, Go, Plus and Pro plans, and developers tested with Developer Mode in ChatGPT.
- Nov 13, 2025. Apps arrived in preview for ChatGPT Business, Enterprise and Edu (OpenAI).
- Dec 18, 2025. "Introducing the app directory" at chatgpt.com/apps: connectors were listed there as apps, and developers could submit apps for review and publication (release notes).
- Jun 18, 2026. App permission controls let users choose "always ask, ask before making changes, or only ask before important changes" (release notes).
- Jul 9, 2026. "We're also replacing the App Directory with the Plugin Directory." Skills became generally available the same day (release notes).
- Sep 29, 2026. Interactive plugin extensions (panels, sidebar views, file viewers and editors) and automations started by MCP events (release notes); at DevDay the same day OpenAI said plugins support the proposed MCP Events spec (Unite.AI).
The name matters for search, not for code: OpenAI's help article now explains that "An app connects ChatGPT to a service, such as Slack. A plugin brings apps and skills together for a task" (Plugins in ChatGPT). An app built with the Apps SDK is one part of a plugin.
What goes into a plugin
OpenAI's Plugins documentation names three parts (Plugins docs, read Nov 6, 2026):
| Part | What it does |
|---|---|
| MCP server | Supplies "live data and controlled tools" |
| Optional UI | UI resources returned from selected MCP tools, shown inside ChatGPT |
| Skills | Repeatable workflows built around the plugin's MCP tools |
A plugin may also run a local MCP server on the user's computer; those are "desktop only" plugins that need the ChatGPT desktop app (Plugins in ChatGPT). Plugins can also include app templates and extensions that open or edit files and show forms; in OpenAI's video on plugin extensions, an extension gives a plugin a persistent home in the sidebar or a side panel beside the conversation.
How to build and publish a ChatGPT plugin
- Build an MCP server that exposes your data and actions as tools (build an MCP server).
- Add optional UI by returning UI resources from the tools that need it (add UI).
- Write skills around those tools (build skills).
- Package the skills and MCP dependencies into a plugin (package your plugin).
- Connect and test it; the quickstart tests the result in ChatGPT Work (connect and test).
- Submit it for review to the ChatGPT Directory, after checking the remote MCP server review requirements and the plugin guidelines (upload and submit). Desktop-only plugins have their own submission page.
For a plugin only you or your workspace will use, there is a shorter path inside ChatGPT: install Plugin Creator and chat with @plugin-creator, or open Plugins > Add (+) (Plugins in ChatGPT). Workspace plugins can use custom MCP apps, and plugins can also be hosted on ChatGPT Sites.
Selling through a plugin
The Plugins docs include a Checkout API for taking payment from a plugin's UI, plus conversion specs for product checkout and restaurant reservations (Checkout API reference). The index read for this page gives no fees or payout terms, so check the reference before planning revenue.
Custom GPTs move to plugins
OpenAI is retiring custom GPTs on Dec 11, 2026 and offers My GPTs > Migrate to plugin: instructions become a skill, connected apps become apps, and knowledge files become reference files, but "GPT custom actions do not transfer" (Help Center). A GPT that relied on custom actions needs an MCP server to keep that ability. Steps are on How to Move Custom GPTs to Plugins and the background on Custom GPTs.
Apps SDK vs the API
The Apps SDK and plugins put your service inside ChatGPT, where ChatGPT's own model and the user's plan pay for the conversation. The OpenAI API, the Responses API and the Agents SDK put OpenAI's models inside your product, billed to you per token. Both can share one MCP server: the Responses API can call remote MCP servers as a tool since May 20, 2025.
Frequently asked questions
Does the ChatGPT Apps SDK still exist? As of Nov 6, 2026, the Apps SDK address at developers.openai.com/apps-sdk opens OpenAI's Plugins documentation, because ChatGPT replaced its App Directory with the Plugin Directory on Jul 9, 2026. Apps built on it still connect, now as parts of plugins.
How do I build a ChatGPT plugin? Build an MCP server with your tools, optionally return UI from some tools, add skills, package them as a plugin, test it in ChatGPT, then submit it to the ChatGPT Directory for review.
Is the Apps SDK based on MCP? Yes. OpenAI described the Apps SDK as an open standard built on the Model Context Protocol, and today's ChatGPT plugins still get their data and tools from MCP servers.
Can I charge money inside a ChatGPT plugin? OpenAI's Plugins documentation includes a Checkout API for taking payment from a plugin's UI. Fees and terms were not in the pages read for this article.
Do custom GPT actions work in plugins? No. OpenAI says GPT custom actions do not transfer when a custom GPT is migrated to a plugin, so that logic has to move to an MCP server.
Sources
- Plugins documentation (Apps SDK address), OpenAI, read Nov 6, 2026
- Build an MCP server, OpenAI, read Nov 6, 2026
- Add UI to your MCP server, OpenAI, read Nov 6, 2026
- Build skills, OpenAI, read Nov 6, 2026
- Package your plugin, OpenAI, read Nov 6, 2026
- Connect and test your plugin, OpenAI, read Nov 6, 2026
- Upload and submit your plugin, OpenAI, read Nov 6, 2026
- Remote MCP server review requirements, OpenAI, read Nov 6, 2026
- Plugin guidelines, OpenAI, read Nov 6, 2026
- Checkout API reference, OpenAI, read Nov 6, 2026
- Introducing apps in ChatGPT, OpenAI, 2025 (updated Nov 13, 2025)
- Plugins in ChatGPT, OpenAI Help Center, read Nov 6, 2026
- Custom GPTs to plugins, article 20001519, OpenAI Help Center, read Nov 6, 2026
- ChatGPT release notes, OpenAI Help Center, read Nov 6, 2026
- Changelog, OpenAI, read Nov 6, 2026
- Build Plugins for ChatGPT, OpenAI, Oct 7, 2026 (video)
- OpenAI unveils GPT-6.1 Sol at DevDay with new Codex and ChatGPT tools, Unite.AI, read Nov 6, 2026
Moments
Build Plugins for ChatGPT
OpenAI
Related
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- API Rate LimitsOpenAI API rate limits depend on your usage tier (Free, Build, Launch or Grow), which rises automatically as total credit purchases reach $5, $100 and $500. On the Build tier GPT-6 Astra allows 5,000 requests and 1,000,000 tokens a minute, and going over returns HTTP 429.
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Batch APIThe OpenAI Batch API runs up to 50,000 requests from one file within 24 hours at 50% off the normal price. Flex processing gives the same discount on ordinary calls that can be slow, Fast mode costs double for quicker answers, and prompt caching cuts the price of repeated prompt prefixes.
- Fine-TuningOpenAI is winding down fine-tuning: the platform is closed to new users, new job creation was restricted on Jul 2, 2026, and existing customers lose job creation on Jan 6, 2027. Fine-tuned models keep serving until their base models are retired, and no GPT-6 model can be fine-tuned.
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OpenAI APIThe OpenAI API lets programs call OpenAI's models (GPT-6 Astra, GPT-6.1 Sol, GPT-6.1 Terra, GPT-6 Luna, image, voice and transcription models) with an API key, billed per token. New projects use the Responses API through the official SDKs, with documentation at developers.openai.com.
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OpenAI API PricingOpenAI API prices are per 1M tokens: GPT-6 Astra costs $10 input and $50 output, GPT-6.1 Sol $2 and $10, GPT-6.1 Terra $1 and $5, and GPT-6 Luna $0.10 and $0.50, as of Nov 6, 2026. Batch and Flex halve those prices, Fast doubles them.
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Realtime APIThe OpenAI Realtime API streams speech in and speech out with low latency over WebRTC or WebSocket, using models such as gpt-realtime-2.1 and the full-duplex GPT-Live 1 ($0.05 a minute), as of Nov 6, 2026. It also handles live transcription and speech-to-speech translation.
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Responses APIThe Responses API is OpenAI's recommended endpoint for new projects, combining model calls, built-in tools, structured outputs and conversation state in one request. Chat Completions is still supported, and the Assistants API it replaced shut down on Aug 26, 2026.
See also
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How to Move Custom GPTs to PluginsCustom GPTs in ChatGPT retire on Dec 11, 2026; to keep one, open My GPTs, select Migrate to plugin, and test the new plugin. Instructions become a skill and knowledge files become reference files, but custom actions and the chosen model do not carry over.
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Custom GPTsCustom GPTs, launched Nov 6, 2023 with the GPT Store following on Jan 10, 2024, retire across ChatGPT on Dec 11, 2026 (Feb 11, 2027 for FedRAMP and approved Enterprise deferrals). Owners can move each GPT into a plugin with Migrate to plugin; old conversations stay readable.