Struct Usage 

pub struct Usage {
    pub input_tokens: u64,
    pub output_tokens: u64,
    pub cached_input_tokens: u64,
}

Three-field token usage as returned by OpenAI’s chat-completion and responses APIs.

Chat Completions exposes the cached count under prompt_tokens_details.cached_tokens; the Responses API uses cached_input_tokens directly. The From impls in this crate flatten both shapes onto these fields.

Fields

input_tokens: u64

Fresh input/prompt tokens (not served from the prompt cache).

output_tokens: u64

Output/completion tokens.

cached_input_tokens: u64

Input tokens that were served from the prompt cache (cache hit).

Implementations

impl Usage

pub fn cache_hit(&self) -> bool

True when the request hit the prompt cache.

pub fn total_tokens(&self) -> u64

Total tokens billed (input + output + cached_input).

pub fn from_chat_completions( prompt_tokens: u64, completion_tokens: u64, cached_tokens: u64, ) -> Self

Build a Usage from a Chat Completions response.

OpenAI reports prompt_tokens as including cached tokens, so we subtract cached_tokens from prompt_tokens to get the fresh input count this struct expects.

pub fn from_responses_api( input_tokens: u64, output_tokens: u64, cached_input_tokens: u64, ) -> Self

Build a Usage from a Responses-API response.

On the Responses API, input_tokens already excludes cached tokens (cached_input_tokens is reported separately).

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 PartialEq for Usage

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Usage

impl Eq for Usage

impl StructuralPartialEq for Usage