1. An engineering team is evaluating a multi-agent ADK trip-planning system. Their trajectory evaluation harness records the full sequence of agent actions and tool calls for each test case. They observe the following pattern: the system achieves a 92% task success rate (correct final itinerary produced), but trajectory analysis reveals that on 40% of successful runs the orchestrator calls the `flight_search` tool three or more times when one call should suffice. Which evaluation dimension does this finding PRIMARILY expose, and what is the MOST appropriate metric to add?
- A. It exposes a retrieval accuracy problem; the team should add a `tool_output_relevance` score to measure whether tool results match the query intent.
- B. It exposes an agent efficiency / step-optimality problem; the team should add a `redundant_tool_call_rate` or `average_tool_calls_per_task` metric to quantify unnecessary actions.✓ Correct
- C. It exposes a task decomposition failure; the team should replace task success rate with a BLEU-score comparison of generated itineraries against reference itineraries.
- D. It exposes a memory leak in ADK's in-session state; the team should add a `session_state_size` metric to monitor how much data is stored per turn.
- E. It exposes a latency regression; the team should instrument end-to-end wall-clock time and set an SLA threshold to catch regressions before deployment.
Explanation
The pattern described — correct output but excess tool invocations — is a classic agent efficiency or step-optimality issue that task success rate alone cannot capture. Adding a `redundant_tool_call_rate` or tracking `average_tool_calls_per_task` via trajectory evaluation directly measures this inefficiency and can surface cost and latency implications. Option A is wrong: the issue is not about tool output relevance (the tool presumably returns correct results); it is about calling the tool too many times. Option C is wrong: BLEU score measures text similarity of outputs, not the efficiency of the action sequence; also replacing task success rate would remove a valuable metric. Option D is wrong: repeated tool calls may bloat session state slightly but the root problem is agent reasoning, not a memory management bug. Option E is wrong: latency is a downstream symptom, not the primary dimension being exposed; adding only a wall-clock SLA does not explain or quantify the root cause of redundant calls.