Skillgrade Graders

---
name: skillgrade-graders
description: Authors deterministic and LLM rubric graders for skillgrade evaluations. Use when creating scoring scripts, writing evaluation rubrics, or combining multiple graders with weighted scoring. Don't use for setting up eval pipelines, configuring eval.yaml defaults, or general test writing.
---

# Skillgrade Grader Authoring

## Procedures

**Step 1: Identify the Grading Strategy**
1. Determine whether the task requires objective verification (deterministic) or qualitative assessment (LLM rubric).
2. For most tasks, combine both: deterministic graders verify outcomes (weight 0.7), LLM rubrics assess approach quality (weight 0.3).

**Step 2: Write a Deterministic Grader**
1. Create a script in the skill's `graders/` directory (bash or TypeScript).
2. The script must output a JSON object to stdout with the following structure:
   ```json
   {"score": 0.67, "details": "2/3 checks passed", "checks": [{"name": "check-name", "passed": true, "message": "Description"}]}
   ```
3. `score` (0.0–1.0) and `details` are required. `checks` is optional but recommended.
4. Read `references/grader-output-schema.md` for the full output specification.
5. Use `awk` for arithmetic in bash scripts — `bc` is not available in `node:20-slim`.
6. Reference the grader in eval.yaml:
   ```yaml
   - type: deterministic
     run: bash graders/check.sh
     weight: 0.7
   ```

**Step 3: Write an LLM Rubric Grader**
1. Draft a rubric with explicit scoring criteria and point allocations.
2. Structure the rubric into weighted sections that sum to 1.0:
   ```
   Workflow Compliance (0-0.5):
   - Did the agent follow the mandatory workflow steps?
   Efficiency (0-0.5):
   - Completed in ≤5 commands without trial-and-error?
   ```
3. Reference the rubric in eval.yaml:
   ```yaml
   - type: llm_rubric
     rubric: |
       [rubric text or file path]
     weight: 0.3
     provider: gemini               # optional: gemini (default) | anthropic | openai
     model: gemini-3-flash-preview  # optional, each provider has a default model
   ```
4. For long rubrics, store in a separate file and reference by path: `rubric: rubrics/quality.md`.

**Step 4: Combine Multiple Graders**
1. Assign weights to each grader based on importance. Weights are normalized automatically.
2. Final reward is calculated as: `Σ (grader_score × weight) / Σ weight`.
3. Example configuration:
   ```yaml
   graders:
     - type: deterministic
       run: bash graders/check.sh
       weight: 0.7
     - type: llm_rubric
       rubric: rubrics/quality.md
       weight: 0.3
   ```

**Step 5: Validate Graders**
1. Create a reference solution script that produces the expected output.
2. Run `skillgrade --validate` to verify graders score the reference solution correctly.
3. Test only deterministic graders: `skillgrade --grader=deterministic` (skips LLM calls, faster iteration).
4. Test only LLM rubric graders: `skillgrade --grader=llm_rubric`.
5. Run a specific eval with a specific grader type: `skillgrade --eval=my-eval --grader=deterministic`.
6. If a grader returns unexpected scores, inspect the script output and adjust scoring logic.

## Error Handling
* If a deterministic grader outputs non-JSON, ensure all `echo`/`console.log` statements except the final JSON result are redirected to stderr.
* If an LLM rubric grader returns 0.00 with a missing API key message, set the appropriate key for your provider: `GEMINI_API_KEY` (provider: gemini), `ANTHROPIC_API_KEY` (provider: anthropic), or `OPENAI_API_KEY` (provider: openai).
* To use a custom/self-hosted LLM endpoint, set `ANTHROPIC_BASE_URL` (for provider: anthropic) or `OPENAI_BASE_URL` (for provider: openai) — e.g. for Ollama or vLLM.
* If scores are inconsistent across trials, reduce rubric ambiguity by adding concrete examples of passing and failing behavior.