Does anyone know what window.openai.callCompletion is?

ChatGPT Apps SDK
1

I’ve been really excited about exploring the possibilities of building apps inside ChatGPT. While digging a bit deeper into the API, I noticed that there are some functions under window.openai that aren’t documented anywhere. One of them is window.openai.callCompletion, which, after some experimenting, I found out seems to be a sampling/createMessage call defined in the MCP documentation.
Ex:

window.openai.callCompletion({
  messages: [{
    role: 'user',
    content: {
      type: 'text',
      text: 'Hello, how are you?'
    }
  }],
  systemPrompt: 'You are a helpful assistant that can answer questions and help with tasks.',
  modelPreferences: {
    hints: [
      { name: 'thinking-high' }
    ]
  },
})

However, this call still doesn’t work and currently returns a 404. But this could be a game changer for app development, since it would theoretically allow you to make sub-agent calls using the user’s own OpenAI account.

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