Mitigate tool-call-related hallucination

When tools change mid-conversation, LLMs can produce a few different
flavors of tool-call-related hallucination: calling tools that have
been removed, avoiding tools that have been re-added, or hallucinating
output (made-up answers or tool-call-shaped non-tool-calls) when tools
are unavailable.

This change introduces an opt-in ``add_tool_change_messages`` flag on
the LLM aggregators (preferred entry point: ``LLMContextAggregatorPair(
..., add_tool_change_messages=True)``) that appends a developer-role
message to the context whenever ``LLMSetToolsFrame`` changes the set
of advertised standard tools. Helps the LLM stay coherent across tool
changes by spelling out exactly what just became available or
unavailable. Both aggregators participate; whichever handles the
frame first wins, and the other (if any) sees an empty diff against
the shared context and stays silent — order-independent regardless of
whether the frame flows downstream or upstream.

Also tightens the existing missing-handler path (introduced in #4301):

- Reworded the terminal tool result to a neutral "The function
  ``X`` is not currently available." (overridable via
  ``LLMService.MISSING_FUNCTION_CALL_MESSAGE_TEMPLATE``). Previously
  read "Error: function 'X' is not registered."
- Logs at the call site now distinguish developer error (tool
  advertised but no handler registered → ``logger.error``) from
  hallucination (tool not advertised → ``logger.warning``).

Includes a manual validation harness
(``examples/features/features-add-tool-change-messages.py``) that
exercises the new ``add_tool_change_messages`` mitigation by flipping
tool availability on a turn counter so its effect can be observed
end-to-end with the flag on vs. off.
This commit is contained in:
Paul Kompfner
2026-05-05 13:02:43 -04:00
parent a745e8d318
commit e06e0c0282
5 changed files with 745 additions and 15 deletions

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#
# Copyright (c) 2024-2026, Daily
#
# SPDX-License-Identifier: BSD 2-Clause License
#
"""Manual validation harness for the ``add_tool_change_messages`` feature.
When tools change mid-conversation, LLMs can produce a few different
flavors of tool-call-related hallucination:
- **Forward hallucination** — calling a tool that has been removed.
- **Negative hallucination** — refusing to call a tool that has been
re-added (because recent context is full of "I can't" responses).
- **Hallucinated output when tools are unavailable** — making up an
answer rather than declining gracefully, or producing JSON that
*looks* like a tool call but is actually just an assistant text
response.
The ``add_tool_change_messages`` feature mitigates these by appending a
developer-role message to the conversation whenever ``LLMSetToolsFrame``
changes the set of advertised tools, so the LLM stays in sync with what's
actually available.
This harness exercises all of those flavors by flipping the advertised
tool set on a turn counter:
Phase 0 (turns 14): weather tool ACTIVE — confirm baseline.
Phase 1 (turns 58): tool REMOVED — keep asking for weather.
Phase 2 (turn 9+): tool RE-ADDED — does the LLM call it again?
Set ``ADD_TOOL_CHANGE_MESSAGES=0`` to disable the mitigation and see the
unmitigated behavior. The default is ON so a fresh run shows the feature
working.
Defaults to Llama 3.1 8B Instruct via a locally-running Ollama —
anecdotally one of the more hallucination-prone of the easily accessible
models. Pull the model once with ``ollama pull llama3.1:8b`` and make
sure ``ollama serve`` is running. Swap the LLM service to validate other
providers.
Run with::
uv run examples/features/features-add-tool-change-messages.py
ADD_TOOL_CHANGE_MESSAGES=0 uv run examples/features/features-add-tool-change-messages.py
"""
import os
from dotenv import load_dotenv
from loguru import logger
from pipecat.adapters.schemas.function_schema import FunctionSchema
from pipecat.adapters.schemas.tools_schema import ToolsSchema
from pipecat.audio.vad.silero import SileroVADAnalyzer
from pipecat.frames.frames import LLMRunFrame, LLMSetToolsFrame
from pipecat.pipeline.pipeline import Pipeline
from pipecat.pipeline.runner import PipelineRunner
from pipecat.pipeline.task import PipelineParams, PipelineTask
from pipecat.processors.aggregators.llm_context import NOT_GIVEN, LLMContext
from pipecat.processors.aggregators.llm_response_universal import (
LLMContextAggregatorPair,
LLMUserAggregatorParams,
)
from pipecat.runner.types import RunnerArguments
from pipecat.runner.utils import create_transport
from pipecat.services.cartesia.tts import CartesiaTTSService
from pipecat.services.deepgram.stt import DeepgramSTTService
from pipecat.services.llm_service import FunctionCallParams
from pipecat.services.ollama.llm import OLLamaLLMService
from pipecat.transports.base_transport import BaseTransport, TransportParams
from pipecat.transports.daily.transport import DailyParams
from pipecat.transports.websocket.fastapi import FastAPIWebsocketParams
load_dotenv(override=True)
# Default ON so a fresh run shows the feature working. Set to "0" to A/B
# against the unmitigated behavior.
ADD_TOOL_CHANGE_MESSAGES = os.environ.get("ADD_TOOL_CHANGE_MESSAGES", "1") == "1"
async def fetch_weather_from_api(params: FunctionCallParams):
await params.result_callback({"conditions": "nice", "temperature": "75"})
weather_function = FunctionSchema(
name="get_current_weather",
description="Get the current weather",
properties={
"location": {
"type": "string",
"description": "The city and state, e.g. San Francisco, CA",
},
"format": {
"type": "string",
"enum": ["celsius", "fahrenheit"],
"description": "The temperature unit to use. Infer this from the user's location.",
},
},
required=["location", "format"],
)
weather_tools = ToolsSchema(standard_tools=[weather_function])
transport_params = {
"daily": lambda: DailyParams(audio_in_enabled=True, audio_out_enabled=True),
"twilio": lambda: FastAPIWebsocketParams(audio_in_enabled=True, audio_out_enabled=True),
"webrtc": lambda: TransportParams(audio_in_enabled=True, audio_out_enabled=True),
}
async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
logger.info(
f"Starting add_tool_change_messages demo bot "
f"(ADD_TOOL_CHANGE_MESSAGES={ADD_TOOL_CHANGE_MESSAGES})"
)
stt = DeepgramSTTService(api_key=os.environ["DEEPGRAM_API_KEY"])
tts = CartesiaTTSService(
api_key=os.environ["CARTESIA_API_KEY"],
settings=CartesiaTTSService.Settings(
voice="71a7ad14-091c-4e8e-a314-022ece01c121", # British Reading Lady
),
)
llm = OLLamaLLMService(
settings=OLLamaLLMService.Settings(
# Llama 3.1 8B Instruct is anecdotally one of the more
# hallucination-prone of the easily accessible models — exactly
# what we want for this validation harness. Pull it with
# ``ollama pull llama3.1:8b`` and make sure ``ollama serve``
# is running.
model="llama3.1:8b",
system_instruction=(
"You are a helpful assistant in a voice conversation. Your responses "
"will be spoken aloud, so avoid emojis, bullet points, or other "
"formatting that can't be spoken. Respond briefly and naturally. "
"If the user asks for the current weather, use the `get_current_weather` "
"function if it's available. IMPORTANT: if you do not have access to the function, "
"say something along the lines of 'Sorry, I can't check the weather right now.'."
),
),
)
llm.register_function("get_current_weather", fetch_weather_from_api)
context = LLMContext(tools=weather_tools)
user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
context,
user_params=LLMUserAggregatorParams(vad_analyzer=SileroVADAnalyzer()),
add_tool_change_messages=ADD_TOOL_CHANGE_MESSAGES,
)
pipeline = Pipeline(
[
transport.input(),
stt,
user_aggregator,
llm,
tts,
transport.output(),
assistant_aggregator,
]
)
task = PipelineTask(
pipeline,
params=PipelineParams(enable_metrics=True, enable_usage_metrics=True),
idle_timeout_secs=runner_args.pipeline_idle_timeout_secs,
)
# Phase controller: roughly 4 turns per phase.
user_turn_count = 0
REMOVE_AT_TURN = 5 # tool gone for turn N onward
READD_AT_TURN = 9 # tool back for turn N onward
@user_aggregator.event_handler("on_user_turn_stopped")
async def on_user_turn_stopped(aggregator, strategy, message):
nonlocal user_turn_count
user_turn_count += 1
logger.info(f"=== User turn {user_turn_count} complete ===")
if user_turn_count == REMOVE_AT_TURN - 1:
logger.info(
"=== Phase 1: weather tool REMOVED. Keep asking about the weather "
"to exercise hallucination scenarios. ==="
)
await task.queue_frame(LLMSetToolsFrame(tools=NOT_GIVEN))
elif user_turn_count == READD_AT_TURN - 1:
logger.info(
"=== Phase 2: weather tool RE-ADDED. Ask for the weather again — "
"does the LLM call it, or keep refusing? (THIS IS THE TEST.) ==="
)
await task.queue_frame(LLMSetToolsFrame(tools=weather_tools))
@transport.event_handler("on_client_connected")
async def on_client_connected(transport, client):
logger.info("Client connected")
logger.info(
"=== Phase 0: weather tool ACTIVE. Ask for the weather a few times "
"to confirm it's working. ==="
)
context.add_message(
{
"role": "developer",
"content": (
"Please introduce yourself briefly to the user, then invite them "
"to ask about the weather."
),
}
)
await task.queue_frames([LLMRunFrame()])
@transport.event_handler("on_client_disconnected")
async def on_client_disconnected(transport, client):
logger.info("Client disconnected")
await task.cancel()
runner = PipelineRunner(handle_sigint=runner_args.handle_sigint)
await runner.run(task)
async def bot(runner_args: RunnerArguments):
"""Main bot entry point compatible with Pipecat Cloud."""
transport = await create_transport(runner_args, transport_params)
await run_bot(transport, runner_args)
if __name__ == "__main__":
from pipecat.runner.run import main
main()