microsoft/semantic-kernel · error · AgentInvokeException

FunctionChoiceBehavior with type '{function_choice_behavior.

Error message

FunctionChoiceBehavior with type '{function_choice_behavior.type_}' is not supported for agent invocations. Use FunctionChoiceBehavior.Auto(filters=...) to control which kernel functions are available.

What it means

Raised when an AzureAIAgent invocation is given a FunctionChoiceBehavior whose type_ is not FunctionChoiceType.AUTO. The Azure AI agent run loop is hardwired to auto-invoke tools, so only the Auto behavior is compatible; other types (None/Required) would hand control to the caller in a way the loop cannot honor.

Source

Thrown at python/semantic_kernel/agents/azure_ai/agent_thread_actions.py:992

            tool["openapi"] = openapi_data
        return tool

    @staticmethod
    def _deduplicate_tools(existing_tools: list[dict], new_tools: list[dict]) -> list[dict]:
        existing_names = {
            tool["function"]["name"] for tool in existing_tools if "function" in tool and "name" in tool["function"]
        }
        return [tool for tool in new_tools if tool.get("function", {}).get("name") not in existing_names]

    @staticmethod
    def _validate_function_choice_behavior(
        function_choice_behavior: FunctionChoiceBehavior | None,
    ) -> None:
        """Validate the function choice behavior is compatible with agent invocations."""
        if function_choice_behavior is None:
            return
        if function_choice_behavior.type_ != FunctionChoiceType.AUTO:
            raise AgentInvokeException(
                f"FunctionChoiceBehavior with type '{function_choice_behavior.type_}' is not supported for agent "
                "invocations. Use FunctionChoiceBehavior.Auto(filters=...) to control which kernel functions "
                "are available."
            )
        if not function_choice_behavior.auto_invoke_kernel_functions:
            raise AgentInvokeException(
                "FunctionChoiceBehavior.Auto(auto_invoke=False) is not supported for agent invocations. "
                "The agent run loop manages tool invocation; disabling auto_invoke is not compatible."
            )
        valid_filter_keys: set[str] = {
            "excluded_plugins",
            "included_plugins",
            "excluded_functions",
            "included_functions",
        }
        if function_choice_behavior.filters is not None:
            if not function_choice_behavior.filters:
                raise AgentInvokeException(

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Switch to FunctionChoiceBehavior.Auto(filters=...) with the desired included_plugins/included_functions/excluded_plugins/excluded_functions to control tool availability.
2. Remove the FunctionChoiceBehavior argument entirely — the agent run loop defaults to exposing all registered kernel functions.
3. If you need required/no-tool semantics, do not use AzureAIAgent; those behaviors are not supported by the hosted run loop.

Example fix

// before
behavior = FunctionChoiceBehavior.Required()
await agent.invoke(thread, messages=..., function_choice_behavior=behavior)

// after
behavior = FunctionChoiceBehavior.Auto(
    filters={"included_functions": ["MyPlugin-MyFunc"]}
)
await agent.invoke(thread, messages=..., function_choice_behavior=behavior)

from semantic_kernel.connectors.ai.function_choice_behavior import FunctionChoiceBehavior, FunctionChoiceType

def is_agent_compatible(behavior) -> bool:
    return behavior is None or behavior.type_ == FunctionChoiceType.AUTO

# before invoking
if not is_agent_compatible(fcb):
    fcb = FunctionChoiceBehavior.Auto()

from semantic_kernel.connectors.ai.function_choice_behavior import FunctionChoiceBehavior, FunctionChoiceType

def is_auto_behavior(b: object) -> bool:
    return (
        b is None
        or (isinstance(b, FunctionChoiceBehavior) and b.type_ == FunctionChoiceType.AUTO)
    )

from semantic_kernel.exceptions import AgentInvokeException

try:
    await agent.invoke(thread, function_choice_behavior=fcb)
except AgentInvokeException as e:
    if "not supported for agent invocations" in str(e):
        fcb = FunctionChoiceBehavior.Auto()
        await agent.invoke(thread, function_choice_behavior=fcb)
    else:
        raise

When it happens

Trigger: Passing FunctionChoiceBehavior.Required() or FunctionChoiceBehavior.NoneInvoke() (or any non-AUTO type) as the function_choice_behavior argument to AzureAIAgent.invoke()/invoke_stream, or setting it on the ChatHistory/PromptExecutionSettings used by the agent.

Common situations: Developer copies a FunctionChoiceBehavior setup from a non-agent chat flow (e.g. ChatCompletionAgent or kernel.invoke_async) into an AzureAIAgent call, expecting the same behavior mapping. Also occurs after upgrading when FunctionChoiceBehavior replaced the older None auto_invoke kwargs.

Related errors

• Unknown filter key(s): {sorted(unknown_keys)}. Valid filter
• FunctionChoiceBehavior.Auto(auto_invoke=False) is not suppor
• FunctionChoiceBehavior filters must not be empty. Provide at
• Missing or malformed 'tool_connections' in: {spec}
• Missing or malformed 'index_name' in: {spec}

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/2eb4b99b8a25e070. Report an issue: GitHub.