Struct Message 

pub struct Message {
    pub id: Option<String>,
    pub role: String,
    pub content: String,
    pub tokens: Option<usize>,
    pub thinking: Option<String>,
    pub streaming: bool,
    pub tool_calls: Option<Vector<ToolCall>>,
    pub tool_name: Option<String>,
    pub image: Option<Arc<PhotonImage>>,
}

A chat message in an LLM conversation.

Represents messages exchanged between users, assistants, and tools in a conversation. Supports various roles (user, assistant, system, tool) and optional features like streaming, thinking traces, and attached images.

Fields

• id - Optional unique identifier for the message
• role - The role of the message sender (“user”, “assistant”, “system”, “tool”)
• content - The text content of the message
• tokens - Optional token count for the message
• thinking - Optional reasoning/thinking trace (for extended thinking models)
• streaming - Whether this is a partial streaming response
• tool_calls - Tool invocations requested by the assistant
• tool_name - Name of the tool (for tool role messages)
• image - Optional attached image (requires “image” feature)

Example

use modular_agent_core::Message;

let user_msg = Message::user("What is the weather?".to_string());
let assistant_msg = Message::assistant("The weather is sunny.".to_string());
let system_msg = Message::system("You are a helpful assistant.".to_string());

Fields

id: Option<String>

Unique identifier for this message.

role: String

Role of the message sender: “user”, “assistant”, “system”, or “tool”.

content: String

Text content of the message.

tokens: Option<usize>

Token count for this message (if available).

thinking: Option<String>

Reasoning/thinking trace for extended thinking models.

streaming: bool

Whether this is a partial streaming response.

tool_calls: Option<Vector<ToolCall>>

Tool calls requested by the assistant in this message.

tool_name: Option<String>

Name of the tool (for tool role messages containing tool results).

image: Option<Arc<PhotonImage>>

Attached image for multimodal messages (requires “image” feature).

Implementations

impl Message

pub fn new(role: String, content: String) -> Self

Creates a new message with the specified role and content.

Arguments

• role - The role of the message sender
• content - The text content of the message

pub fn assistant(content: String) -> Self

Creates an assistant message with the given content.

pub fn system(content: String) -> Self

Creates a system message with the given content.

System messages typically set the behavior or context for the assistant.

pub fn user(content: String) -> Self

Creates a user message with the given content.

pub fn tool(tool_name: String, content: String) -> Self

Creates a tool response message.

Tool messages contain the result of a tool call and are associated with a specific tool by name.

Arguments

• tool_name - The name of the tool that produced this result
• content - The tool’s output/result as a string

pub fn with_image(self, image: Arc<PhotonImage>) -> Self

Attaches an image to this message (builder pattern).

Only available when the “image” feature is enabled.

Trait Implementations

impl Clone for Message

fn clone(&self) -> Message

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Message

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Message

fn default() -> Message

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Message

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<Message> for AgentValue

fn from(msg: Message) -> Self

Converts to this type from the input type.

impl PartialEq for Message

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Message

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl TryFrom<AgentValue> for Message

type Error = AgentError

The type returned in the event of a conversion error.

fn try_from(value: AgentValue) -> Result<Self, Self::Error>

Performs the conversion.