OptionalextraAdditional input tokens the character-based estimators cannot see
(v3.7) — e.g. provider-side cost of tool schemas kept outside
messages, or media priced by out-of-band rules. Built-in
estimators add this verbatim to their input estimate; custom
estimators may honor or ignore it.
Must be a non-negative integer when present. Participates in the default deduplication key like any other request field, so requests differing only here are never conflated.
Optionalmax_OptionalmodelOptionalsystemOptional system prompt (v3.7). Counted by the built-in estimators
exactly like message content: a plain string, or an array of content
blocks (text blocks counted by characters, non-text blocks subject
to the model-aware estimator's opaqueBlockTokens surcharge).
Before v3.7, callers had to fold the system prompt into a synthetic message for it to participate in estimation — which also distorted events, logs, and deduplication keys. Carry it here instead.
Minimal request shape.
modelis optional at the request level. When present, the estimator uses it for ratio lookup instead of the bulkhead-level default. This supports A/B testing, canary deployments, and mixed-model routing through a single bulkhead.