API Platform: Arrow 2, Open Responses, and sandbox keys

QuiverAI's API now has a POST /v1/responses endpoint compatible with stock Open Responses clients. You can declare function and custom tools, then execute function_call items yourself. The endpoint is stateless: previous_response_id and store: true are rejected.

Arrow 2 and Arrow 2 Telos use measured token billing rather than fixed credits, with rates available as billing.rates on GET /v1/models.

Sandbox keys let you test the same routes without reaching a model. They return deterministic output marked x-quiver-environment: test, and support deliberately slowing streamed responses to test timeout handling.