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Documentation Index

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Google ADK

A native ADK extension is on the roadmap. The pattern below uses ADK’s public callback hooks.

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Install

pip install fact0 google-adk

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Pattern

Register before_model_callback / after_model_callback to emit spans. 
import fact0
from google.adk.agents import LlmAgent
from google.adk.runners import Runner

client = fact0.Client(api_key="alk_live_...")

def before_model(ctx, request):
    ex = client.telemetry.current_execution()
    ctx.state["_lf_span"] = ex.start_span(
        "model.invoke", span_type="MODEL_INVOCATION",
    )

def after_model(ctx, response):
    span = ctx.state.pop("_lf_span", None)
    if span is not None:
        span.complete(output={"text": getattr(response, "text", "")[:500]})

agent = LlmAgent(
    name="researcher",
    model="gemini-2.0-flash",
    before_model_callback=before_model,
    after_model_callback=after_model,
)

with client.telemetry.execution(agent_id="adk.researcher") as ex:
    runner = Runner(agent=agent, app_name="research", session_service=...)
    for event in runner.run(user_id="u1", session_id="s1", new_message=...):
        ...

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Tool callbacks

ADK also exposes before_tool_callback and after_tool_callback — wrap them the same way and tag the span as TOOL_CALL.