Enum Tokenizer 

pub enum Tokenizer {
    Heuristic,
    Cl100kBase,
    O200kBase,
}

Tokenizer choice for token counting.

Heuristic is the fast char-based approximation. The *Base variants load a real BPE table once and produce exact counts that match the model provider’s billing.

Variants

Heuristic

chars / 3.5 approximation. ±20% accuracy.

Cl100kBase

cl100k_base: GPT-3.5-turbo / GPT-4 / Claude (older).

O200kBase

o200k_base: GPT-4o / GPT-4o-mini / Claude (current Anthropic models reportedly share this family on the o200k axis).

Implementations

impl Tokenizer

pub fn count(&self, text: &str) -> usize

Count tokens in text using the selected tokenizer.

On failure to load a BPE table at first use, the variant degrades to Self::Heuristic silently (with a one-time WARN log). Better an over-conservative estimate than a panic in the MCP hot path.

pub fn as_str(&self) -> &'static str

Stable identifier for telemetry / config serialization.

pub fn from_str_lossy(s: &str) -> Self

Parse from telemetry / config string. Unknown values fall back to Heuristic to keep startup non-fatal on typos.

Trait Implementations

impl Clone for Tokenizer

fn clone(&self) -> Tokenizer

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Tokenizer

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

Formats the value using the given formatter.

impl Default for Tokenizer

fn default() -> Tokenizer

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Tokenizer

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Tokenizer

fn eq(&self, other: &Tokenizer) -> 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 Serialize for Tokenizer

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Tokenizer

impl Eq for Tokenizer

impl StructuralPartialEq for Tokenizer