Message

A message represents a single round of information in a model conversation. The message definition is:

class FunctionCall(TypedDict, total=False):
    name: str
    arguments: Union[str, Dict[str, Any]]

class ToolCall(TypedDict, total=False):
    id: str
    type: Literal['function']
    function: FunctionCall

class Message(TypedDict, total=False):
    role: Literal['system', 'user', 'assistant', 'tool']
    type: str
    content: Union[str, List[Dict[str, str]]]
    tool_calls: List[ToolCall]
    tool_call_id: str
    reasoning_content: str
    images: Optional[List[Union[str, Any]]]
    videos: Optional[List[Union[str, Any]]]
    audios: Optional[List[Union[str, Any]]]

Essentially, Message is a Dict. It contains several fields, with the following being strongly relevant to developers:

role: Message type, including four types: ‘system’, ‘user’, ‘assistant’, ‘tool’.
- system: System instruction message, only appears in the 0th message
- user: User input message
- assistant: Model reply message
- tool: Tool call result, similar to user message input to the model
content: Message body, if it contains multimodal information, then placeholders are needed:
- : Image placeholder

<image>The image shows a grassland with three rabbits on it.

tool_calls: Tool call list, information output by the model to the user, usually parsed from the content corresponding to assistant.
- ToolCall matches the OpenAI chat-completion schema: the outer dict is {type: "function", function: {...}}, with the tool name at function.name. arguments must be a dict at chat-template render time (dispatch also accepts a JSON string).
images: Original image information contained in the message
videos: Original video information contained in the message
audios: Original audio information contained in the message