To sum things up, In Chicago style, you must credit ChatGPT when you reproduce its words within your own work, but unless you include a publicly available URL, that information should be put in the text or in a note—not in a bibliography or reference list. Other AI-generated text can be cited similarly. 

Chicago style recommends citing AI tolls such as ChatGPT or Microsoft Copilot in a footnote entry NOT a Bibliography entry

Footnote or endnote Format:

1. Text generated by ChatGPT, March 31, 2023, OpenAI, https://chat.openai.com.

If the prompt has not been included in the body of the text, it can be included in the note:

1. ChatGPT, response to “Explain how to make pizza dough from common household ingredients,” OpenAI, March 7, 2023.

Author-Date Format:

If you’re using author-date instead of footnotes or endnotes, any information not provided  in the body of the text would be placed in a parenthetical text reference. For example,

(ChatGPT, March 7, 2023).