openAIChat with custom BaseURL sends unsupported parameters to non-OpenAI providers

[toshiakit]

When using openAIChat with a custom BaseURL to connect to OpenAI-compatible endpoints (e.g., Google Gemini), the request fails because the toolbox always includes parameters like frequency_penalty, presence_penalty, and top_p in the request body — even at their default values (0, 0, 1).

Some OpenAI-compatible providers reject unknown fields. For example, Gemini returns:

Server returned error indicating: "Invalid JSON payload received. Unknown name "frequency_penalty": Cannot find field."

Steps to reproduce:

chat = openAIChat("You are a helpful assistant", ...
      ModelName="gemini-2.5-flash", ...                                                                                                                   
      APIKey=getenv("GEMINI_API_KEY"), ...                                                                                                                
      BaseURL="https://generativelanguage.googleapis.com/v1beta/openai");
messages = messageHistory;                                                                                                                              
messages = addUserMessage(messages, "Hello");                                                                                                           
generate(chat, messages); 

Root cause:

In +llms/+internal/buildAzureParameters.m, the mapNVPToParameters loop (lines 48–52) includes any parameter where ~isempty(nvp.(opt)) is true. Since 0 and 1 are not empty, default values for frequency_penalty, presence_penalty, and top_p are always sent.

Suggested fix:

Skip parameters that are at their default/neutral values (e.g., frequency_penalty=0, presence_penalty=0, top_p=1) so they are omitted from the request body. Alternatively, provide an option to control which parameters are included in the request.

Environment:

• MATLAB R2025b
• LLMs with MATLAB v4.8.0

[debymf]

Thanks for the detailed report and repro, this is super helpful!
We’ll look into updating this so default/neutral parameters are omitted (or making it configurable). Appreciate you flagging this!

[toshiakit]

Perhaps one question I have is, it feels strange to access Gemini using openAIChat interface. Perhaps we may want genericAIChat interface? It could be a super-class of openAIChat.

[debymf]

The focus of openAIChat is to connect to OpenAI compatible APIs, but we will consider something more generic in the future. Thanks for the suggestion!