english/.opencode/skills/skill-creator/references/eval-infrastructure-guide.md

Eval Infrastructure Guide

Quantitative skill evaluation using parallel testing, grading, and human-in-the-loop feedback.

Overview

Eval infrastructure tests skills via:

1. Trigger accuracy — Does skill activate on correct queries?
2. Output quality — Do outputs meet assertions?
3. Performance comparison — With-skill vs baseline metrics

Workspace Structure

<skill-name>-workspace/
├── iteration-1/
│   ├── eval-0-descriptive-name/
│   │   ├── with_skill/outputs/
│   │   ├── without_skill/outputs/
│   │   └── eval_metadata.json
│   ├── eval-1-another-test/
│   ├── benchmark.json
│   ├── benchmark.md
│   └── timing.json
├── iteration-2/
└── feedback.json

Step-by-Step Evaluation

1. Create Test Cases

Write evals/evals.json:

{
  "skill_name": "my-skill",
  "evals": [
    {
      "id": 0,
      "prompt": "User task description",
      "expected_output": "What correct output looks like",
      "files": [],
      "assertions": [
        {"id": "a-1", "text": "Output is valid JSON"},
        {"id": "a-2", "text": "All input rows present in output"}
      ]
    }
  ]
}

2. Spawn Parallel Runs (CRITICAL)

MUST spawn with-skill AND baseline runs simultaneously in same turn.

• Sequential spawning = unfair timing comparison
• Capture timing data from subagent notifications immediately (only opportunity)
• Draft assertions while runs execute

3. Grade Outputs

Use grader agent template (agents/grader.md):

• Evaluates outputs against assertions
• Returns pass/fail with evidence for each assertion
• Output: grading.json

4. Aggregate Results

Run scripts/aggregate_benchmark.py:

• Consolidates multiple run results
• Calculates mean, stddev, min, max per metric
• Generates benchmark.json + benchmark.md

5. Launch Viewer

Run scripts/generate_review.py:

• Interactive HTML with two tabs:
  • Outputs — qualitative review, feedback textbox, prev/next
  • Benchmark — quantitative metrics, analyst observations
• Auto-saves feedback to feedback.json

6. Iterate

Read feedback.json, generalize from patterns:

• Don't overfit to test examples
• Keep prompts lean — remove ineffective instructions
• Scale test set to 5-10 cases for production skills

Assertion Design

Good (objective, discriminating):

• "Output is valid JSON"
• "All input rows present in output"
• "Execution completes in <5 seconds"

Bad (subjective, non-discriminating):

• "Output is well-written" (subjective)
• "Skill executes" (passes with or without skill)
• "Output file exists" (too vague)

Performance Metrics

Metric	Description
pass_rate	% of assertions passing (0.0-1.0)
tokens_used	Total input+output tokens
execution_time_ms	Wall-clock duration
tool_calls	Number of tool invocations
files_created	Output file count

Expected improvements:

• Code generation: +40-70% pass rate, -20-30% tokens
• Data processing: +50-80% pass rate, -30-50% time
• Analysis: +30-50% pass rate

Environment Adaptations

Claude Code (Full)

• Spawn parallel with+without runs
• Full benchmarking + viewer
• Description optimization available

Claude.ai (No subagents)

• Run tests sequentially
• Skip baseline runs
• Skip quantitative benchmarking

Cowork (No browser)

• Use --static <output_path> for standalone HTML
• Download feedback.json from viewer