Google Agent Platform Eval Flywheel

Agent Platform Eval Flywheel Skill

Help users evaluate and iteratively improve GenAI models and agents using the Agent Platform GenAI Evaluation SDK (google.genai / agentplatform).

When to use this skill

• Evaluating GenAI agents or models with the Agent Platform GenAI Evaluation SDK (client.evals.evaluate()).
• Creating evaluation datasets from session traces, pandas DataFrames, or synthetic generation.
• Selecting, configuring, or writing custom evaluation metrics.
• Analyzing rubric verdicts, loss patterns, and clustering failures.
• Suggesting concrete code/prompt improvements based on eval results.

Setup

Install the SDK:

pip install google-cloud-aiplatform[evaluation]>=1.154.0 google-genai>=1.0.0

Need GOOGLE_CLOUD_PROJECT and GOOGLE_CLOUD_LOCATION. Check env vars first; if missing, ask the user. Newer Gemini models often need location="global".

The Quality Flywheel

Five stages, run in order on the first pass, then loop 2 → 5 until quality targets are met.

Shortcuts that waste time

1. Prepare Data

Produce an EvaluationDataset. There are three input shapes, pick the one that matches the data the user already has:

• EvalCase list (single-turn or multi-turn):

  from agentplatform import types
  dataset = types.EvaluationDataset(eval_cases=[
      types.EvalCase(prompt="What is 2+2?", response="4", reference="4"),
      # For multi-turn agent traces, set agent_data instead of prompt/response.
  ])
  

  Multi-turn agent traces wrap each conversation in AgentData → ConversationTurn → AgentEvent. See references/dataset_schema.md for the full type hierarchy.

• Pandas DataFrame (tabular sources — CSV, BigQuery, Sheets):

  import pandas as pd
  from agentplatform import types
  
  df = pd.DataFrame({
      "prompt":    ["What is 2+2?", "Capital of France?"],
      "response":  ["4",            "Paris"],
      "reference": ["4",            "Paris"],
  })
  dataset = types.EvaluationDataset(eval_dataset_df=df)
  

  Column names must match the fields the chosen metrics expect (see references/dataset_schema.md for the per-metric requirements table).

• Cold start (no data at all): synthesize scenarios server-side with client.evals.generate_user_scenarios(...) and a UserScenarioGenerationConfig (user_scenario_count, simulation_instruction, environment_data). Stage 2 plays them out.

For ADK session dumps, use scripts/parse_adk_traces.py instead of writing the conversion by hand.

2. Run Inference

Populate responses/traces on the dataset. Skip this stage if traces are already complete (e.g., production logs or replay).

# Agent eval — pass a callable wrapping the user's ADK Agent/App.
client.evals.run_inference(model=agent_callable, src=dataset)

# Model eval — pass a model ID directly.
client.evals.run_inference(model="gemini-2.5-flash", src=dataset)

# Synthesized scenarios — let the simulator drive.
client.evals.run_inference(
    model=agent_callable,
    src=dataset,
    user_simulator_config=UserSimulatorConfig(max_turn=10),
)

# DataFrame also works as src= — no EvalCase wrapping needed.
client.evals.run_inference(model="gemini-2.5-flash", src=df)

3. Grade (always run)

result = client.evals.evaluate(dataset=dataset, metrics=[...])

Pick metrics by what you want to measure. Full catalog in references/metric_registry.md.

Agent metrics (multi-turn, adaptive rubrics) — start here for agent eval.

General quality metrics (single-turn, adaptive rubrics) — for model eval.

Static rubric metrics (fixed criteria) — apply alongside the above.

Domain-specific check no built-in covers: write a custom metric.

• Predefined: types.RubricMetric.<NAME> — server-side AutoRater, no judge model needed.
• Custom LLM-as-a-judge: types.LLMMetric with prompt_template or types.MetricPromptBuilder for structured rubrics.
• Custom code: types.CodeExecutionMetric with a custom_function string containing def evaluate(instance: dict) for remote sandboxed execution; or types.Metric with custom_function=<callable> for local execution.

Always persist the result so Stage 4 and 5 can read it. Save both JSON (machine-readable, diffable) and HTML (human-readable, linkable):

import datetime
from pathlib import Path

from agentplatform._genai import _evals_visualization

out_dir = Path("artifacts/grade_results")
out_dir.mkdir(parents=True, exist_ok=True)
ts = datetime.datetime.now().strftime("%Y%m%d_%H%M%S")

result_json = result.model_dump_json()
(out_dir / f"results_{ts}.json").write_text(result_json)

html = _evals_visualization.get_evaluation_html(result_json)
(out_dir / f"results_{ts}.html").write_text(str(html))

Or after the fact: scripts/render_html_report.py --type evaluation or scripts/inspect_results.py --save-html.

4. Analyze Failures

Read summary_metrics and eval_case_results — never fabricate scores. Use scripts/inspect_results.py --failing-only to filter to failures.

For each failed metric, see references/failure_patterns.md for deeper diagnoses. The compact mapping:

For 10+ failures on the same metric, use the Error Analysis service to cluster failures into themes (L1/L2 taxonomy categories) instead of reading every trace:

# Only supports multi_turn_task_success and multi_turn_tool_use_quality.
# Service runs in the global region.
analysis_client = agentplatform.Client(project="PROJECT_ID", location="global")
response = analysis_client.evals.generate_loss_clusters(
    eval_result=result,
    metric="multi_turn_task_success",
    config={"max_top_cluster_count": 5},
)
for r in response.results:
    for cluster in r.clusters:
        print(
            f"[{cluster.taxonomy_entry.l1_category}/"
            f"{cluster.taxonomy_entry.l2_category}] "
            f"{cluster.item_count} cases — {cluster.taxonomy_entry.description}"
        )

Save response.model_dump_json() and render with scripts/render_html_report.py --type loss-analysis.

5. Optimize & Iterate

Apply a fix targeting the failing metric. Re-run Stage 3. Compare with scripts/compare_results.py --baseline <prev> --candidate <new> to confirm the target improved AND no other metric regressed.

Track progress across iterations:

Expect 5–10+ iterations per failing case. Only after a case passes should you expand coverage with more eval cases.

Proving your work

Never claim eval results you didn't read from an actual result object.

• After running eval, print the summary_metrics table (scripts/inspect_results.py).
• After a fix, show before/after via scripts/compare_results.py.
• Before declaring success, confirm ALL cases pass — not just the one you were working on.

If you can't produce the evidence (SDK call failed, result truncated, metric unsupported), say so explicitly. Don't paper over gaps.

Rules of Engagement

1. Always Plan First: Before writing a script, output a <plan> block detailing the steps you are about to take.
2. Step-by-Step Execution: Write the script, execute it, wait for output, then analyze. Don't do everything in one response.
3. Standard Python: Use standard Python imports (import agentplatform, from google.genai import types). Don't use internal import paths.
4. Verify Before Guessing: When unsure about SDK types or metrics, check the SDK source code rather than guessing or hallucinating.

SDK Quick Reference

import agentplatform
from agentplatform import types
from google.genai import types as genai_types
import pandas as pd

# Initialize client
client = agentplatform.Client(project="PROJECT_ID", location="LOCATION")

# --- SINGLE-TURN EVAL (EvalCase list) ---
dataset = types.EvaluationDataset(eval_cases=[
    types.EvalCase(prompt="Query here", response="Model response here"),
])

# --- SINGLE-TURN EVAL (pandas DataFrame) ---
df = pd.DataFrame({
    "prompt":   ["Q1", "Q2"],
    "response": ["A1", "A2"],
})
dataset = types.EvaluationDataset(eval_dataset_df=df)

# --- MULTI-TURN AGENT EVAL ---
agent_data = types.evals.AgentData(
    agents={"my_agent": types.evals.AgentConfig(
        agent_id="my_agent", instruction="You are helpful.")},
    turns=[types.evals.ConversationTurn(turn_index=0, events=[
        types.evals.AgentEvent(author="user",
            content=genai_types.Content(role="user",
                parts=[genai_types.Part(text="Hello")])),
        types.evals.AgentEvent(author="my_agent",
            content=genai_types.Content(role="model",
                parts=[genai_types.Part(text="Hi! How can I help?")])),
    ])],
)
dataset = types.EvaluationDataset(
    eval_cases=[types.EvalCase(agent_data=agent_data)])

# --- METRICS ---
predefined = types.RubricMetric.MULTI_TURN_TRAJECTORY_QUALITY
custom_llm = types.LLMMetric(name="tone",
    prompt_template="Is this polite? Response: {response}")
custom_code = types.CodeExecutionMetric(name="check",
    custom_function='def evaluate(instance): return {"score": 1.0}')

# --- EVALUATE ---
result = client.evals.evaluate(dataset=dataset, metrics=[predefined])

# --- RESULTS ---
for s in result.summary_metrics:
    print(f"{s.metric_name}: mean={s.mean_score}, pass_rate={s.pass_rate}")
for case in result.eval_case_results:
    for cand in case.response_candidate_results:
        for name, r in cand.metric_results.items():
            print(f"  {name}: score={r.score}, explanation={r.explanation}")

See references/sdk_patterns.md for advanced patterns: synthetic data generation, pairwise comparison, MetricPromptBuilder, multi-agent evaluation.

Bundled scripts