Invalid input: expected an array with minimum length 1, but received an empty array.

The error you are encountering, "Invalid 'messages.tool_calls': empty array. Expected an array with minimum length 1, but got an empty array instead," is due to the following reasons:

• Required Field: The tool_calls field in the messages array is a required parameter for the OpenAI API, particularly for certain models like GPT-4. The API expects this field to contain at least one element, but in your case, it is empty.

• API Request Structure: The error indicates that the structure of your API request does not match the expected format. Specifically, the messages array item at index 4 does not have a valid tool_calls array, which is necessary for the API to process the request correctly.

This issue arises because the API is strictly enforcing the presence of tool_calls in the request payload, and an empty array does not meet this requirement.