Struct Message 

pub struct Message {
    pub id: Uuid,
    pub conversation_id: Uuid,
    pub role: MessageRole,
    pub content: String,
    pub metadata: HashMap<String, Value>,
    pub timestamp: DateTime<Utc>,
    pub tool_calls: SmallVec<[ToolCall; 2]>,
    pub tool_call_id: Option<String>,
    pub name: Option<String>,
}

A single message in a conversation.

Messages have a role (system, user, assistant, or tool), content, and optional metadata. Tool calls are validated to only appear on assistant messages.

Fields

id: Uuid

Unique identifier for this message.

conversation_id: Uuid

ID of the conversation this message belongs to.

role: MessageRole

The role of the message sender.

content: String

The text content of the message.

metadata: HashMap<String, Value>

Application-specific metadata.

timestamp: DateTime<Utc>

When this message was created.

tool_calls: SmallVec<[ToolCall; 2]>

Tool calls requested by this message (assistant messages only, uses SmallVec to avoid allocations for ≤2 calls).

tool_call_id: Option<String>

Tool call ID this message responds to (required for tool messages).

name: Option<String>

Function name (required for tool messages).

Implementations

impl Message

pub fn builder() -> MessageBuilder<((), (), (), (), (), (), (), (), ())>

Create a builder for building Message. On the builder, call .id(...)(optional), .conversation_id(...), .role(...), .content(...), .metadata(...)(optional), .timestamp(...)(optional), .tool_calls(...)(optional), .tool_call_id(...)(optional), .name(...)(optional) to set the values of the fields. Finally, call .build() to create the instance of Message.

impl Message

pub fn new( conversation_id: Uuid, role: MessageRole, content: impl Into<String>, ) -> Self

Creates a new message with the specified role and content.

pub fn system(conversation_id: Uuid, content: impl Into<String>) -> Self

Creates a new system message.

pub fn user(conversation_id: Uuid, content: impl Into<String>) -> Self

Creates a new user message.

pub fn assistant(conversation_id: Uuid, content: impl Into<String>) -> Self

Creates a new assistant message.

pub fn tool( conversation_id: Uuid, content: impl Into<String>, tool_call_id: String, function_name: String, ) -> Result<Self>

Creates a new tool result message.

Arguments

• conversation_id - The conversation this message belongs to
• content - The result/output from the tool execution
• tool_call_id - The ID of the tool call this responds to
• function_name - The name of the function that was called

Errors

Returns an error if the tool_call_id is empty.

pub fn with_metadata(self, key: impl Into<String>, value: Value) -> Self

Adds a metadata key-value pair to this message.

pub fn with_metadata_typed<T: Serialize>( self, key: impl Into<String>, value: T, ) -> Result<Self>

Adds a metadata key-value pair to this message with automatic serialization.

This is a convenience method that accepts any serializable type.

pub fn with_tool_calls( self, tool_calls: impl Into<SmallVec<[ToolCall; 2]>>, ) -> Result<Self>

Sets the tool calls for this message.

Errors

Returns an error if this message is not an assistant message.

pub fn add_tool_call(&mut self, tool_call: ToolCall) -> Result<()>

Adds a single tool call to this message.

Errors

Returns an error if this message is not an assistant message.

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<'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 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.