Realtime API: Incorrect Realtime Item Type with tool_choice: {type: "function", name: "my_function"}})

API Bugs
,
1

Expected Behavior:

When calling client.updateSession({tool_choice: {type: "function", name: "list_emails"}}), the function list_emails should be invoked correctly, similar to the behavior when using client.updateSession({tool_choice: "auto"}). This includes:

  1. A realtime.item of type function_call being generated with the correct arguments.
  2. A function_call_output type item returned with the processed data.
  3. Audio output in response to the function’s execution.

Here is an example for the working case using (tool_choice: "auto"):

Initial User Message:

{
    "id": "item_AY81IkN6zZ0We2KwXkd8B",
    "object": "realtime.item",
    "type": "message",
    "status": "completed",
    "role": "user",
    "content": [
        {
            "type": "input_text",
            "text": "Hello! Check my last email and reply to it."
        }
    ],
    "formatted": {
        "audio": {},
        "text": "Hello! Check my last email and reply to it.",
        "transcript": ""
    }
}

AI Audio Response:

{
    "id": "item_AY81IaiSORg9pH7Vr0WEr",
    "object": "realtime.item",
    "type": "message",
    "status": "completed",
    "role": "assistant",
    "content": [
        {
            "type": "audio",
            "transcript": "Sure! I'll check your latest email and get a reply ready. Please give me a moment."
        }
    ],
    "formatted": {
        "audio": {},
        "text": "Hello! Check my last email and reply to it.",
        "transcript": ""
    }
}

Function Call:

{
    "id": "item_AY81KpMatEHuAxWRNIwLa",
    "object": "realtime.item",
    "type": "function_call",
    "status": "completed",
    "name": "list_emails",
    "call_id": "call_I14Ukrd5RS2gtfY8",
    "arguments": "{\"numEmails\":1}",
    "formatted": {
        "audio": {},
        "text": "",
        "transcript": "",
        "tool": {
            "type": "function",
            "name": "list_emails",
            "call_id": "call_I14Ukrd5RS2gtfY8",
            "arguments": "{\"numEmails\":1}"
        }
    }
}

Function Call Output:

{
    "id": "item_AY81MM9OwvmT4v8KAuQbx",
    "object": "realtime.item",
    "type": "function_call_output",
    "call_id": "call_I14Ukrd5RS2gtfY8",
    "output": " [data retrieved] ",
    "formatted": {
        "audio": {},
        "text": "",
        "transcript": "",
        "output": " [data retrieved] "
    },
    "status": "completed"
}

Incorrect Behavior

using client.updateSession({tool_choice: {type: "function", name: "list_emails"}})

Initial User Message:

{
    "id": "item_AY8B7XZfNVik3T9v6vJ7C",
    "object": "realtime.item",
    "type": "message",
    "status": "completed",
    "role": "user",
    "content": [
        {
            "type": "input_text",
            "text": "Hello! Check my last email and reply to it."
        }
    ],
    "formatted": {
        "audio": {},
        "text": "Hello! Check my last email and reply to it.",
        "transcript": ""
    }
}

Argument Passed as message instead of function_call (numEmails = 1):

{
    "id": "item_AY8B7KuSqtPRwh1Y7HStO",
    "object": "realtime.item",
    "type": "message",
    "status": "completed",
    "role": "assistant",
    "content": [
        {
            "type": "text",
            "text": "{\"numEmails\":1}"
        }
    ],
    "formatted": {
        "audio": {},
        "text": "{\"numEmails\":1}",
        "transcript": ""
    }
}

Repeated Argument Item (Still Incorrect Type):

{
    "id": "item_AY8B8DN1mW7Rgp0r3dEbY",
    "object": "realtime.item",
    "type": "message",
    "status": "completed",
    "role": "assistant",
    "content": [
        {
            "type": "text",
            "text": "{\"numEmails\":1}"
        }
    ],
    "formatted": {
        "audio": {},
        "text": "{\"numEmails\":1}",
        "transcript": ""
    }
}

Missing Audio Output:

Unlike the auto case, no audio output is generated.

Summary of the Issue:

When forcing a function call with client.updateSession({tool_choice: {type: “function”, name: “list_emails”}}):

The function_call type is not used for the generated realtime.item.

The arguments appear as message type instead of being passed correctly as a function_call type.

No audio output is generated, contrary to the behavior with tool_choice: “auto”.

I’m using the openai-realtime-api-beta typescript library from GitHub - openai/openai-realtime-api-beta: Node.js + JavaScript reference client for the Realtime API (beta)

How can I fix that?