Struct Usage 

pub struct Usage {
    pub prompt_tokens: Option<u32>,
    pub completion_tokens: Option<u32>,
    pub total_tokens: Option<u32>,
    pub reasoning_tokens: Option<u32>,
    pub cache_read_tokens: Option<u32>,
    pub cache_write_tokens: Option<u32>,
    pub cost_usd: Option<f64>,
    pub stop_reason: Option<String>,
}

Token usage information from a model response.

Providers should emit this at the end of each response stream. Token counts and costs are optional since not all providers report them.

Fields

prompt_tokens: Option<u32>

Number of tokens in the prompt/input.

completion_tokens: Option<u32>

Number of tokens in the completion/output.

total_tokens: Option<u32>

Total tokens (prompt + completion).

reasoning_tokens: Option<u32>

Tokens used for reasoning/thinking (for reasoning models).

cache_read_tokens: Option<u32>

Tokens read from cache (for providers with prompt caching).

cache_write_tokens: Option<u32>

Tokens written to cache.

cost_usd: Option<f64>

Estimated cost in USD for this request.

stop_reason: Option<String>

Provider-specific reason the generation stopped (e.g. stop, length, tool_use).

Implementations

impl Usage

pub const fn new(prompt_tokens: u32, completion_tokens: u32) -> Self

Creates a new usage with basic token counts.

pub const fn with_reasoning_tokens(self, tokens: u32) -> Self

Adds reasoning token count.

pub const fn with_cache_tokens(self, read: u32, write: u32) -> Self

Adds cache token counts.

pub const fn with_cost(self, cost_usd: f64) -> Self

Adds estimated cost.

pub fn with_stop_reason(self, reason: impl Into<String>) -> Self

Adds provider stop reason metadata.

pub fn accumulate(&mut self, other: &Self)

Accumulates usage from another instance.

Trait Implementations

impl Clone for Usage

fn clone(&self) -> Usage

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Usage

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

Formats the value using the given formatter.

impl Default for Usage

fn default() -> Usage

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Usage

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Usage

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for Usage

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Usage