> ## Documentation Index > Fetch the complete documentation index at: https://openrouter.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # PricingSource Who bills the engine's calls beyond the model's tokens: `openrouter` (the `pricing` rows, from the caller's credits), `provider` (a per-call tool fee from the model's provider on the inference call, at its own rates), `byok` (the engine's vendor, against the caller's own key), or `none` (no charge) ## Example Usage ```python theme={null} from openrouter.components import PricingSource # Open enum: unrecognized values are captured as UnrecognizedStr value: PricingSource = "openrouter" ``` ## Values This is an open enum. Unrecognized values will not fail type checks. * `"openrouter"` * `"provider"` * `"byok"` * `"none"`