Enum ToolLoopEvent 

pub enum ToolLoopEvent {
    IterationStart {
        iteration: u32,
        message_count: usize,
    },
    ToolExecutionStart {
        call_id: String,
        tool_name: String,
        arguments: Value,
    },
    ToolExecutionEnd {
        call_id: String,
        tool_name: String,
        result: ToolResult,
        duration: Duration,
    },
    LlmResponseReceived {
        iteration: u32,
        has_tool_calls: bool,
        text_length: usize,
    },
    LoopDetected {
        tool_name: String,
        consecutive_count: u32,
        action: LoopAction,
    },
}

Events emitted during tool loop execution for observability.

These events allow UIs to show real-time progress:

• “Iteration 3 starting”
• “Calling tool search…”
• “Tool search completed in 200ms”

Example

use llm_stack::tool::{ToolLoopConfig, ToolLoopEvent};
use std::sync::Arc;

let config = ToolLoopConfig {
    on_event: Some(Arc::new(|event| {
        match event {
            ToolLoopEvent::IterationStart { iteration, .. } => {
                println!("Starting iteration {iteration}");
            }
            ToolLoopEvent::ToolExecutionStart { tool_name, .. } => {
                println!("Calling {tool_name}...");
            }
            ToolLoopEvent::ToolExecutionEnd { tool_name, duration, .. } => {
                println!("{tool_name} completed in {duration:?}");
            }
            _ => {}
        }
    })),
    ..Default::default()
};

Variants

IterationStart

A new iteration of the tool loop is starting.

Fields

iteration: u32

The iteration number (1-indexed).

message_count: usize

Number of messages in the conversation so far.

ToolExecutionStart

About to execute a tool.

Fields

call_id: String

The tool call ID from the LLM.

tool_name: String

Name of the tool being called.

arguments: Value

Arguments passed to the tool.

ToolExecutionEnd

Tool execution completed.

Fields

call_id: String

The tool call ID from the LLM.

tool_name: String

Name of the tool that was called.

result: ToolResult

The result from the tool.

duration: Duration

How long the tool took to execute.

LlmResponseReceived

LLM response received for this iteration.

Fields

iteration: u32

The iteration number (1-indexed).

has_tool_calls: bool

Whether the response contains tool calls.

text_length: usize

Length of any text content in the response.

LoopDetected

A tool call loop was detected.

Emitted when the same tool is called with identical arguments for threshold consecutive times. Only emitted when LoopDetectionConfig is configured.

Fields

tool_name: String

Name of the tool being called repeatedly.

consecutive_count: u32

Number of consecutive identical calls detected.

action: LoopAction

The action being taken in response.

Trait Implementations

impl Clone for ToolLoopEvent

fn clone(&self) -> ToolLoopEvent

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ToolLoopEvent

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.