Trait Agent 

pub trait Agent: Send + Sync {
    // Required methods
    fn name(&self) -> &str;
    fn description(&self) -> &str;
    fn sub_agents(&self) -> &[Arc<dyn Agent>];
    fn run<'life0, 'async_trait>(
        &'life0 self,
        ctx: Arc<dyn InvocationContext>,
    ) -> Pin<Box<dyn Future<Output = Result<EventStream>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;

    // Provided method
    fn supports_agent_transfer(&self) -> bool { ... }
}

The fundamental trait for all ADK agents.

Every agent — whether a simple LLM wrapper, a multi-step workflow, or a composite orchestrator — implements this trait. The runtime invokes run with an InvocationContext and consumes the returned EventStream.

Required Methods

fn name(&self) -> &str

Returns the unique name of this agent.

fn description(&self) -> &str

Returns a human-readable description of this agent’s purpose.

fn sub_agents(&self) -> &[Arc<dyn Agent>]

Returns the child agents managed by this agent.

fn run<'life0, 'async_trait>( &'life0 self, ctx: Arc<dyn InvocationContext>, ) -> Pin<Box<dyn Future<Output = Result<EventStream>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Executes the agent and returns a stream of events.

Provided Methods

fn supports_agent_transfer(&self) -> bool

Whether this agent participates in LLM-driven agent transfer and may be resumed directly across conversation turns.

When a session persists across turns, the runner inspects history to decide which agent should handle the next user message. LLM-based and custom agents return the default true, so the runner can hand a new turn back to whichever agent responded last.

Deterministic workflow agents (sequential, parallel, loop, conditional) override this to return false. Their sub-agents must not be resumed individually: doing so would skip the workflow’s other sub-agents on subsequent turns. Returning false makes the runner resume the workflow root instead, so every sub-agent runs again on each turn.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors