Struct Message 

pub struct Message {
    pub id: MessageId,
    pub role: MessageRole,
    pub parts: Vec<Part>,
    pub task_id: Option<TaskId>,
    pub context_id: Option<ContextId>,
    pub reference_task_ids: Option<Vec<TaskId>>,
    pub extensions: Option<Vec<String>>,
    pub metadata: Option<Value>,
}

A message exchanged between a client and an agent.

Fields

id: MessageId

Unique message identifier.

role: MessageRole

Role of the message originator.

parts: Vec<Part>

Message content parts.

Spec requirement: Must contain at least one element. The A2A protocol does not define behavior for empty parts lists.

Parsing treats absence as empty (ProtoJSON printers omit empty repeated fields; the gRPC binding already decodes it that way) — the server rejects empty parts with a structured invalid-params error instead of a JSON type error, uniformly across bindings.

task_id: Option<TaskId>

Task this message belongs to, if any.

context_id: Option<ContextId>

Conversation context this message belongs to, if any.

reference_task_ids: Option<Vec<TaskId>>

IDs of tasks referenced by this message.

extensions: Option<Vec<String>>

URIs of extensions used in this message.

metadata: Option<Value>

Arbitrary metadata.

Implementations

impl Message

pub fn text(&self) -> Option<&str>

Returns the text of the first text Part, or None if this message carries no text part.

Reading the caller’s text is the most common operation in agent code. This is the one-liner form of the parts.iter().find_map(..) match over PartContent::Text:

use a2a_protocol_types::message::{Message, MessageId, MessageRole, Part};

let msg = Message {
    id: MessageId::new("m1"),
    role: MessageRole::User,
    parts: vec![Part::url("https://example.com/f.pdf"), Part::text("hello")],
    task_id: None,
    context_id: None,
    reference_task_ids: None,
    extensions: None,
    metadata: None,
};

assert_eq!(msg.text(), Some("hello"));

Non-text parts are skipped rather than ending the search, so a message that leads with a file attachment still yields its text.

pub fn texts(&self) -> impl Iterator<Item = &str>

Returns the text of every text Part, in order, skipping non-text parts.

Use this when a message may carry several text parts and Message::text would silently drop all but the first.

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<(), Error>

Formats the value using the given formatter.

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

fn deserialize<__D>( __deserializer: __D, ) -> Result<Message, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for Message

impl PartialEq for Message

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for Message

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Message

impl TryFrom<Message> for Message

type Error = ConvertError

The type returned in the event of a conversion error.

fn try_from( value: Message, ) -> Result<Message, <Message as TryFrom<Message>>::Error>

Performs the conversion.

impl TryFrom<Message> for Message

type Error = ConvertError

The type returned in the event of a conversion error.

fn try_from( value: Message, ) -> Result<Message, <Message as TryFrom<Message>>::Error>

Performs the conversion.