Liu 2023 Agentbench

SKILL: AgentBench - Evaluating and Debugging LLM Agents

DECISION POINTS

Model Selection for Agent Tasks

IF task requires procedural execution (web shopping, DB queries, API calls):
  ├─ IF <15 steps AND template-based outputs
  │  └─ Use code-trained models (CodeLlama) - 3x better at format compliance
  └─ IF >15 steps OR requires plan revision
     └─ Use general models (GPT-4) - maintains coherence across turns

IF task requires strategic reasoning (games, puzzles, negotiations):
  ├─ IF model must generate novel hypotheses
  │  └─ Avoid code-trained models - they over-optimize for deterministic paths
  └─ IF model must revise plans based on feedback
     └─ Use frontier models only - others lose state after round 5

IF failure budget <10%:
  ├─ Invalid format/action rate matters more than success rate
  └─ API models (GPT-4: 6% invalid) vs Open source (13.6% invalid)

IF task involves >20 interaction rounds:
  └─ Only GPT-4 tier maintains plan-state binding - others enter loops by round 10

Failure Diagnosis Decision Tree

IF agent produces malformed outputs despite clear instructions:
  ├─ Check Rouge-L similarity in last 3 outputs
  │  ├─ High (>0.8): Loop detection failure → Add state tracking
  │  └─ Low (<0.5): Executive function gap → Add format validation
  
IF agent violates environment rules (impossible actions):
  ├─ Count rule violations per environment type
  │  ├─ Code environments: Missing API constraints → Add action space docs
  │  ├─ Game environments: Invalid moves → Add rule reminders each turn  
  │  └─ Web environments: Element targeting → Add DOM structure context

IF agent exceeds task limits without completion:
  ├─ Analyze final 5 rounds for repetition patterns
  │  ├─ Repeating same action: Add "what have I tried?" prompt
  │  ├─ Repeating same reasoning: Add progress checkpoints
  │  └─ Random actions: Escalate to human or abort task

Prompt Engineering Verbosity Trade-off

IF environment has complex rule set (>10 constraints):
  ├─ High verbosity: Include full rules every turn
  │  └─ Trade-off: Context bloat but lower invalid action rate
  └─ Low verbosity: Rules in system message only
     └─ Trade-off: Cleaner prompt but higher rule violation risk

IF task requires >10 sequential steps:
  ├─ Include explicit progress tracking: "Step X of Y completed"
  └─ Add loop detection: "Have I done this exact action before?"

FAILURE MODES

1. Rubber Stamp Validation ("Format Looks Right")

Detection Rule: If model produces structurally valid JSON but semantically invalid actions (e.g., {"action": "click", "element": "nonexistent_button"})

Symptoms:

• Valid syntax, impossible actions
• Model explains action correctly but targets wrong elements
• High invalid action rate (>15%) despite format compliance

Diagnosis: Dissociation between linguistic understanding and environmental grounding

Fix: Add action pre-validation layer that checks element existence before execution

2. Planning Amnesia ("I Had a Plan, What Was It?")

Detection Rule: If model generates good initial plan but actions don't follow plan by round 5+ OR model repeats plan generation mid-task

Symptoms:

• Rouge-L <0.3 between plan and actual action sequence
• Model re-explains same strategy when asked mid-task
• Good reasoning in <thought> tags, contradictory actions

Diagnosis: Plan-state binding failure in working memory

Fix: Include plan summary in every prompt; add "current plan step" tracking

3. Metacognitive Blindness ("I'm Not Stuck")

Detection Rule: If Rouge-L ≥0.8 in final 3 rounds AND task incomplete

Symptoms:

• Repeating identical actions/reasoning
• No recognition of loop when explicitly asked
• Confidence remains high despite lack of progress

Diagnosis: No internal representation of "attempted strategies" or progress monitoring

Fix: External loop detection with mandatory strategy pivot after 3 identical rounds

4. Code Training Rigidity ("There Must Be One Right Sequence")

Detection Rule: If code-trained model fails strategic tasks with success rate <50% of general model performance

Symptoms:

• Over-optimization for deterministic execution
• Fails to explore alternative paths when first approach fails
• Strong performance on procedural tasks, weak on exploratory tasks

Diagnosis: Code training bias toward single optimal path

Fix: Use general models for strategic tasks; add explicit exploration prompts for code-trained models

5. Executive Function Collapse ("I Know What To Do But Can't Do It")

Detection Rule: If model correctly explains requirements when asked but immediately violates them in output

Symptoms:

• Perfect task understanding in conversation mode
• Immediate format violations in action mode
• Can debug own errors but repeats them

Diagnosis: Linguistic competence vs. procedural compliance dissociation

Fix: Constrained decoding, output validation layer, or format templates with variable substitution

WORKED EXAMPLES

Example 1: Web Shopping Failure Analysis

Scenario: Agent must purchase specific laptop from e-commerce site. CodeLlama-34b vs GPT-4 comparison.

Turn 1-3: Both models navigate homepage correctly, use search function

• CodeLlama: Clean JSON format, efficient navigation
• GPT-4: Slightly verbose but same actions

Turn 4-6: Product comparison required

• CodeLlama: Attempts to add first matching product to cart immediately
• GPT-4: Opens multiple products, compares specs against requirements

Turn 7-12: CodeLlama hits constraint (wrong specs)

• CodeLlama: Loops on same product, doesn't revise search strategy
• GPT-4: Recognizes mismatch, refines search with different keywords

Turn 13+: Task completion

• CodeLlama: Task limit exceeded (TLE) - Rouge-L 0.87 in final rounds
• GPT-4: Completes purchase successfully

Key Insight: Procedural task (web navigation) initially favors CodeLlama, but strategic pivot requirement (spec mismatch → search refinement) causes failure. The task grounding shifted from procedural to strategic mid-execution.

Example 2: Debug TLE Loop with Recovery

Scenario: Agent stuck in navigation loop on unfamiliar website

Detection Phase:

Round 15: {"action": "click", "element": "nav-menu"}
Round 16: {"action": "click", "element": "nav-menu"}  
Round 17: {"action": "click", "element": "nav-menu"}
Rouge-L: 0.92 - LOOP DETECTED

Recovery Steps:

1. Interrupt: Insert "You've clicked nav-menu 3 times. What are you trying to accomplish?"
2. State Reset: Agent responds: "Looking for product categories"
3. Alternative Prompt: "List 3 different ways to find product categories besides nav-menu"
4. Strategy Pivot: Agent suggests search bar, footer links, homepage scan
5. Execution: Agent successfully uses search bar, completes task

Key Insight: Loop detection must trigger strategy enumeration, not just "try harder." The fix is metacognitive scaffolding, not better reasoning.

QUALITY GATES

• Invalid format rate <8% (measure malformed JSON/action structures)
• Invalid action rate <12% (measure environment rule violations)
• Task limit exceeded rate <30% (measure incomplete tasks at round limit)
• Loop detection triggers activated <15% of runs (Rouge-L ≥0.8 check)
• Multi-turn coherence maintained: Rouge-L between plan and actions ≥0.4 after round 10
• Model-task grounding alignment: Code-trained models only on procedural tasks
• Failure mode distribution logged: Track format/action/TLE breakdown for intervention targeting
• Human escalation triggers defined: Automatic handoff rules for detected failure patterns
• Progress validation: State advancement measurable every 5 rounds
• Environment-specific constraints validated: Action space limitations enforced pre-execution

NOT-FOR BOUNDARIES

Do NOT use this skill for:

• Single-turn question answering → Use question-answering-strategies.md instead
• Static text generation → Use content-generation-patterns.md instead
• Pure reasoning without environmental interaction → Use logical-reasoning-frameworks.md instead
• Real-time reactive systems → Use streaming-response-handling.md instead
• Simple API calls without multi-step planning → Use api-integration-patterns.md instead

Delegate to other skills when:

• Task requires domain-specific knowledge → Use domain-expertise-routing.md
• Evaluation needs custom metrics → Use benchmark-design-principles.md
• Agent architecture design needed → Use agent-orchestration-patterns.md
• Production deployment concerns → Use llm-system-monitoring.md

This skill specifically handles: Multi-round interactive decision-making where environmental constraints, plan revision, and failure recovery are primary concerns.