Struct UsageTracker 

pub struct UsageTracker { /* private fields */ }

Accumulates token usage and execution statistics over a single task run.

The default task handlers create one UsageTracker per task, thread it through run_tool_loop, and - when usage metadata is enabled - merge metadata into the task’s metadata field once the task reaches a terminal state.

Counters are split into two groups:

• Token usage (prompt_tokens / completion_tokens / total_tokens), summed from each CompletionUsage the gateway returns. Every add_token_usage call also bumps an internal llm_calls counter so metadata can decide whether a usage block is meaningful.
• Execution stats (iterations / messages / tool_calls / failed_tools), counted as the agent loop runs.

All mutators take &self (interior mutability via a Mutex) so the tracker can be shared behind a shared reference across .await points.

Implementations

impl UsageTracker

pub fn new() -> Self

pub fn add_token_usage(&self, usage: &CompletionUsage)

Add the token counts from one chat-completion response and record that an LLM call was made.

pub fn increment_iteration(&self)

Count one pass through the agent’s model ↔ tool loop.

pub fn add_messages(&self, count: usize)

Count count conversation messages produced during the loop (the default handlers use this for tool-result messages fed back to the model).

pub fn increment_tool_calls(&self)

Count one dispatched tool call.

pub fn increment_failed_tools(&self)

Count one tool call that failed (missing handler or handler error).

pub fn has_usage(&self) -> bool

Whether anything worth reporting was recorded. Mirrors the Go ADK: true when at least one LLM call, iteration, message, or tool call happened.

pub fn metadata(&self) -> Map<String, Value>

Build the metadata object merged into a terminal task. Always emits an execution_stats block; only emits a usage block when at least one LLM call contributed token counts (otherwise the zeros would be misleading).

Trait Implementations

impl Debug for UsageTracker

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

Formats the value using the given formatter.

impl Default for UsageTracker

fn default() -> UsageTracker

Returns the “default value” for a type.