Invalid response received: Please ensure multiturn requests end with a user role or a function response.

The 400 Bad Request error you are encountering in the Google API, specifically with the message "Please ensure that multiturn requests ends with a user role or a function response," is likely due to the following reasons:

Incorrect Request Format

The request you are sending does not conform to the expected format. Specifically, multiturn requests (which involve multiple interactions or turns in a conversation) must be properly structured and must end with either a user role or a function response. This error indicates that the request is missing the required final response or is not formatted correctly according to the API's specifications[3>.

Missing Required Parameters

The error message suggests that a required parameter or response type is missing. In the context of multiturn requests, this could mean that the request does not include the necessary user role or function response that the API expects to complete the interaction successfully.

Invalid Argument

The "INVALID_ARGUMENT" status indicates that the arguments or parameters provided in the request are not valid or do not meet the API's requirements. This could be due to incorrect formatting, missing fields, or incorrect data types.