Struct Message

Source

pub struct Message {
    pub role: MessageRole,
    pub content: Vec<ContentBlock>,
}

Expand description

A complete message in a conversation.

Each message has a role and a sequence of text, image, tool-call, or tool-result blocks.

§Message Patterns

§Simple Text Message

use open_agent::Message;

let msg = Message::user("What's the weather?");

§Assistant Response with Tool Call

use open_agent::{Message, ContentBlock, TextBlock, ToolUseBlock};
use serde_json::json;

let msg = Message::assistant(vec![
    ContentBlock::Text(TextBlock::new("Let me check that for you.")),
    ContentBlock::ToolUse(ToolUseBlock::new(
        "call_123",
        "get_weather",
        json!({"location": "San Francisco"})
    ))
]);

§Tool Result

use open_agent::{Message, ContentBlock, ToolResultBlock};
use serde_json::json;

let msg = Message::user_with_blocks(vec![
    ContentBlock::ToolResult(ToolResultBlock::new(
        "call_123",
        json!({"temp": 72, "conditions": "sunny"})
    ))
]);

Fields§

§role: MessageRole

The role/sender of this message.

§content: Vec<ContentBlock>

The content blocks that make up this message.

A message can contain multiple blocks of different types. For example, an assistant message might have both text and tool use blocks.

Implementations§

Source §

impl Message

Source

pub fn new(role: MessageRole, content: Vec<ContentBlock>) -> Self

Creates a message with the supplied role and content blocks.

Source

pub fn user(text: impl Into<String>) -> Self

Creates a user message containing one text block.

Source

pub fn assistant(content: Vec<ContentBlock>) -> Self

Creates an assistant message with the supplied text and/or tool-call blocks.

Source

pub fn system(text: impl Into<String>) -> Self

Creates a system message containing one text block.

Source

pub fn user_with_blocks(content: Vec<ContentBlock>) -> Self

Creates a user message with arbitrary blocks, including tool results.

See Message for a tool-result example.

Source

pub fn user_with_image( text: impl Into<String>, image_url: impl Into<String>, ) -> Result<Self>

Creates a user message with text and an image from a URL.

This is a convenience method for the common pattern of sending text with an image. The image uses ImageDetail::Auto by default. For more control over detail level, use user_with_image_detail().

§Arguments

text - The text prompt
image_url - URL of the image (http/https or data URI)

§Errors

Returns Error::InvalidInput if the image URL is invalid (empty, wrong scheme, etc.)

§Example

use open_agent::Message;

let msg = Message::user_with_image(
    "What's in this image?",
    "https://example.com/photo.jpg"
)?;

Source

pub fn user_with_image_detail( text: impl Into<String>, image_url: impl Into<String>, detail: ImageDetail, ) -> Result<Self>

Creates a user message with text and an image with specified detail level.

Detail is a provider hint; its effect on quality and token costs depends on the endpoint and model.

§Arguments

text - The text prompt
image_url - URL of the image (http/https or data URI)
detail - Detail level (Low, High, or Auto)

§Errors

Returns Error::InvalidInput if the image URL is invalid (empty, wrong scheme, etc.)

§Example

use open_agent::{Message, ImageDetail};

let msg = Message::user_with_image_detail(
    "Analyze this diagram in detail",
    "https://example.com/diagram.png",
    ImageDetail::High
)?;

Source

pub fn user_with_base64_image( text: impl Into<String>, base64_data: impl AsRef<str>, mime_type: impl AsRef<str>, ) -> Result<Self>

Creates a user message with text and a base64-encoded image.

This is useful when you have image data in memory and want to send it without uploading to a URL first. The image will be encoded as a data URI.

§Arguments

text - The text prompt
base64_data - Base64-encoded image data
mime_type - MIME type (e.g., “image/png”, “image/jpeg”)

§Errors

Returns Error::InvalidInput if the base64 data or MIME type is invalid

§Example

use open_agent::Message;

// Use properly formatted base64 (length divisible by 4, valid chars)
let base64_data = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==";
let msg = Message::user_with_base64_image(
    "What's this image?",
    base64_data,
    "image/png"
)?;