microsoft/semantic-kernel · error · ValueError

Tool message must have a function result content item.

Error message

Tool message must have a function result content item.

What it means

Raised inside _format_tool_message when a tool-role ChatMessageContent has no items that are instances of FunctionResultContent. The Ollama API expects tool messages to carry a function result; the formatter extracts the result from the first FunctionResultContent item. Without one, it cannot build the payload. Raised as a plain ValueError.

Source

Thrown at python/semantic_kernel/connectors/ai/ollama/services/utils.py:102

            }
            for tool_call in tool_calls
        ]

    return assistant_message


def _format_tool_message(message: ChatMessageContent) -> Message:
    """Format a tool message to the expected object for the client.

    Args:
        message: The tool message.

    Returns:
        The formatted tool message.
    """
    function_result_items = [item for item in message.items if isinstance(item, FunctionResultContent)]
    if not function_result_items:
        raise ValueError("Tool message must have a function result content item.")

    return Message(role="tool", content=str(function_result_items[0].result))


MESSAGE_CONVERTERS: dict[AuthorRole, Callable[[ChatMessageContent], Message]] = {
    AuthorRole.SYSTEM: _format_system_message,
    AuthorRole.USER: _format_user_message,
    AuthorRole.ASSISTANT: _format_assistant_message,
    AuthorRole.TOOL: _format_tool_message,
}


def update_settings_from_function_choice_configuration(
    function_choice_configuration: "FunctionCallChoiceConfiguration",
    settings: "PromptExecutionSettings",
    type: FunctionChoiceType,
) -> None:
    """Update the settings from a FunctionChoiceConfiguration.

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Ensure tool messages contain at least one FunctionResultContent item
2. Use FunctionResultContent(id=..., name=..., result=...) when constructing tool responses
3. Check message.items before adding the message to chat history

Example fix

// before
ChatMessageContent(role=AuthorRole.TOOL, items=[TextContent(text='42')])
// after
ChatMessageContent(role=AuthorRole.TOOL, items=[FunctionResultContent(id='call_1', name='calc', result='42')])

from semantic_kernel.contents import FunctionResultContent

def validate_tool_message(message):
    has_result = any(
        isinstance(item, FunctionResultContent) for item in message.items
    )
    if not has_result:
        raise ValueError('Tool message must contain a FunctionResultContent item')

from semantic_kernel.contents import FunctionResultContent

def is_valid_tool_message(message) -> bool:
    return any(
        isinstance(item, FunctionResultContent) for item in message.items
    )

try:
    response = await chat.get_chat_message_contents(chat_history=history, settings=settings)
except ValueError as e:
    if 'function result content item' in str(e):
        logger.error('A tool message is missing its FunctionResultContent; rebuilding')
        raise

When it happens

Trigger: Constructing a ChatMessageContent with role=AuthorRole.TOOL but with items that do not include a FunctionResultContent — e.g. only TextContent items, or an empty items list. Triggered during message formatting for any Ollama request containing a tool message.

Common situations: Manually building tool responses instead of using the function-calling result pipeline; serializing/deserializing tool messages and losing the FunctionResultContent type; adding a TextContent to a tool message by mistake.

Related errors

• Image item must contain data encoded as base64.
• Image must be encoded as base64.
• Please provide valid Ollama configuration in appsettings.Dev
• No function result provided in the tool message.
• No IOllamaApiClient implementations found in the service col

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/bff02b213834c2b6. Report an issue: GitHub.