Lessons learnt from speedrunning ChatGPT Apps

ChatGPT Apps SDK
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I have been speedrunning for 10 days with a bunch of small ChatGPT Apps to experiment + see whats possible. So freaking fun and exciting :rocket:

Didn’t really fit the picture of a full on “app” in ChatGPT (more like POCs) but just wanted to share what I’ve done so you can see what you can do + get my lessons learnt from it all and what potentially OpenAI can do in the Apps SDK.

Lessons Learnt

Since things are moving so quickly, maybe some of the following has been fixed already, feel free to lmk!

  • CSP does not support anything other than https, for example, if I wanted to permit wss://example.com/ws, the Apps SDK would set this to be https://wss://example.com/ws
  • Write tool calls are not supported on mobile apps
  • Mobile PIP potentially makes the PIP window disappear on a subsequent tool call that does not render a widget
  • Since all widgets + resources and loaded at connection time, you have to make sure you wait for the render data to finish loading up. It would be great in the future for the Apps SDK to support rendering widgets from the response of the tool call itself, saving us the round trip from the render data (more aligned with MCP-UI)

Apps

Tech Used + Advice

  • Cloudflare for MCP hosting
  • React Server Components for widget resources using RedwoodSDK - this was a huge win for me for DX, didn’t need a separate build step, can render from tool response directly versus waiting for render data (MCP-UI approach) when it is supported
  • Optional - MCP-UI - Used MCP-UI to support other clients as well, but not required for ChatGPT Apps
  • Overall, don’t need to overthink, you can do any typical frontend setup + tools + frameworks here for Apps SDK

I haven’t felt so excited in a while. Apps in ChatGPT is really the future tbh. And Apps SDK was really well thought out.

1 Like
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Thank you for your sharing, it’s cool that you’ve built so many apps so fast!

interesting, do you mind elaborating more on what you meant by “at connection time” and “wait[ing] for the render data to finish loading up”? More specifically, if I’m understanding it right, at which point in time during the component render phase after an MCP tool call do these correspond to? Why is saving the round trip from render data going to be a significant performance improvement?

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On another unrelated note, how did you record those crisp demo videos on those Twitter X posts? I like the part where you zoomed into specific areas of the screen. Those showcased your ChatGPT apps really clearly and I thought to learn from that.