Struct AgentBuilder 

pub struct AgentBuilder { /* private fields */ }

Builds an Agent.

An Agent is lightweight configuration — no infrastructure, no session. All runtime concerns are injected at call time via &AgentRuntime or &mut AgentRuntime.

Example

let agent = Agent::builder()
    .system_prompt("You are a helpful assistant.")
    .on_token(|t| print!("{t}"))
    .build();

Implementations

impl AgentBuilder

pub fn new() -> Self

pub fn system_prompt(self, prompt: impl Into<String>) -> Self

A system-level prompt that prefixes every interaction.

pub fn on_token<F>(self, f: F) -> Self

where F: Fn(String) + Send + Sync + 'static,

Fired for each text token streamed from the LLM.

pub fn on_tool_call<F>(self, f: F) -> Self

where F: Fn(String, Value) + Send + Sync + 'static,

Fired when a tool call is detected (before execution).

pub fn on_tool_result<F>(self, f: F) -> Self

where F: Fn(String, Result<String, String>) + Send + Sync + 'static,

Fired when a tool execution completes.

pub fn on_turn_start<F>(self, f: F) -> Self

where F: Fn() + Send + Sync + 'static,

Fired at the start of each ReAct turn.

pub fn on_turn_end<F>(self, f: F) -> Self

where F: Fn() + Send + Sync + 'static,

Fired at the end of each ReAct turn.

pub fn on_event<F>(self, f: F) -> Self

where F: Fn(AgentEvent) + Send + Sync + 'static,

Fired for every AgentEvent (catch-all).

pub fn build(self) -> Agent

Build the Agent.

Trait Implementations

impl Default for AgentBuilder

fn default() -> Self

Returns the “default value” for a type.