Empirical testing showed the previous design — grafting a verbose
re-invocation reminder into the payload's `description` field for
started and intermediate messages — was actually making Nova Sonic
*worse*, not better: more spurious re-invocations of the same tool,
not fewer. Plausibly the long, instruction-shaped description text
reads as content the model has to respond to, where a terse status
update reads as ambient state.
Replace the reminder grafting with a caller-supplied `template`
keyword argument on `prepare_message_payload_for_realtime`. When
`None` (the default), the payload is serialized to its canonical
JSON form. When provided, `template.format(tool_call_id=…, status=…,
result=…, description=…)` is applied. The template is honored across
all kinds, so callers route per kind based on which wire channel
they're using.
Nova Sonic now defines its own bracketed plain-text template
(`_ASYNC_TOOL_RESULT_TEXT_TEMPLATE`) and applies it on the
cross-modal user-text channel (intermediate / final). The started
path stays on raw JSON (the formal AWS tool-result channel requires
valid JSON). A code comment at the template constant captures the
empirical finding for the next person — short framing yields much
better behavior, surprising as it sounds.
Tests updated for the new template behavior across all kinds. Also
reverts a stream-tool example sleep-duration tweak (20s → 10s) and
adds a commented-out alternative in the function-calling-openai-async-stream
example for parallel testing.
9a8cd5cee5