Separate provider rejection from caller clarification

In a Pipecat tool-only voice flow, a provider request rejection must not become an unlimited request for the caller to repeat information. Validate the complete outbound tool bundle under the serving API's strict-schema rules: optional business fields need nullable schemas when every property must be required. A single invalid unused tool can reject the entire request before inference. Route deterministic schema errors to bounded service-failure recovery, and distinguish backend-generated recovery actions from actual model tool calls in traces. A returned recovery transition must also be executed. These measures address request validity and failure containment; they do not establish improved caller satisfaction. Applies when: tool-only voice pipelines turn missing model output into clarification speech. Keywords: Pipecat OpenAI Responses strict schema optional nullable recovery voice attribution