session.run(), on top of the prompt options.
Properties
string | false
The output-format instructions appended to the prompt as an extra text
block when
output is set. Pass a string to replace the default, or
false to append nothing (e.g. when the prompt already explains the
expected JSON).unknown
JSON Schema describing
output, embedded in the appended output-format
instructions so the agent knows the exact shape to produce. Rarely
needed: when omitted, the SDK derives it from the schema itself — via a
toJsonSchema() / toJSONSchema() method on the schema object (e.g.
arktype), the Standard JSON Schema extension (~standard.jsonSchema), or
on Node z.toJSONSchema() for zod 4 schemas (zod-to-json-schema for
zod 3, when installed). Pass this to override the derived schema or when
derivation isn’t possible — e.g. zod 4.1 or older on an edge runtime.Record<string, unknown>
Extra
_meta to send with the prompt (see PromptOptions).StandardSchema<T>
Type:
StandardSchemaSchema for the turn’s structured output (any Standard Schema, e.g. zod).
run() appends output-format instructions to the prompt (see
RunOptions.instructions); the final agent message is parsed as
JSON — either the whole message or its last ```json fenced block — and
validated; the result lands on outcome.output. Validation failure
rejects the turn. A turn that stops without end_turn (cancelled,
refusal, …) still resolves, but reading its output throws.AbortSignal
Cancel the turn as soon as this signal aborts (see
PromptOptions).