strands.decisions.decision_model

Base interface for making structured “decisions” from inside the SDK.

DecisionModel

class DecisionModel(abc.ABC)

Defined in: src/strands/decisions/decision_model.py:16

Abstract base for anything that can answer closed questions.

The public ask opens a decision span, validates the question map, delegates to the subclass _ask, records usage, the question ids, and the answer set as span attributes, and closes the span. Content goes on span attributes rather than span events because OpenTelemetry has deprecated the span-event recording API. Every implementation is traced identically. Given an invocation_context, ask also adds the reported usage to that request once _ask returns.

ask

async def ask(state: DecisionInput,
              questions: dict[str, Question],
              *,
              invocation_context: InvocationContext | None = None,
              **kwargs: Any) -> DecisionResult

Defined in: src/strands/decisions/decision_model.py:27

Ask one or more closed questions over the given state.

Arguments:

state - A plain string, a one-shot content list, or a message history.
questions - Map of identifier to question. The returned answers dict is keyed off this same map.
invocation_context - Request to add this decision’s token usage to. The request’s limits do not apply to the decision.
**kwargs - Additional keyword arguments forwarded to the implementation for future extensibility.

Returns:

A DecisionResult whose answers are keyed by the question identifiers.

Raises:

ValueError - If questions is empty or a question violates its semantic constraints.
TypeError - If invocation_context was not created by the SDK.
StructuredOutputException - If the model declines to produce a valid answer set, omits an answer, or returns a value outside a question’s allowed choices.