Improve Skill Quality

Turn a failing or unconvincing evaluation into a targeted fix. The single most common mistake in this repo is rewriting skill prose in response to a verdict whose real cause was the eval, the fixtures, or the harness. Classify first, then fix.

When to Use

• An evaluation verdict is a regression, underpowered, or "no credible improvement".
• A skill wins in the isolated arm but not in the plugin arm, or is reported "not activated".
• /evaluate reports "Evaluation ran but produced no results".
• A skill scores well but costs too much (tokens, turns, wall time, plugin menu budget).
• Deciding whether to strengthen or retire a persistently weak skill.

When Not to Use

• Creating a new skill from scratch — use create-skill.
• Creating a new eval.yaml from scratch — use create-skill-test.
• Changing the harness itself (eng/skill-validator, eng/vally-adapter, evaluation*.yml).

Inputs

Workflow

Step 1: Get the evidence before forming a hypothesis

Read InvestigatingResults.md for how to download artifacts and read results.json. Extract, per failing stimulus:

• win / tie / loss record and total trials (trials = stimuli × runs)
• activation status in the isolated and plugin arms, separately
• the judge's verbatim reason on each losing trial
• whether any trial errored, timed out, or produced empty output

Do not change skill content until you can quote a losing trial and the judge's reason for it. For the other cause classes the evidence is different: harness failures are diagnosed from the job log and the spec, and power problems from the trial record — neither has a losing trial to quote, and demanding one is what sends people rewriting prose instead.

Step 2: Classify the failure

Work down this table and stop at the first row that matches. Rows are ordered by how often the symptom has been misdiagnosed as a skill-content problem — the fixture row is first because a fixture failure also presents as a setup or reliability failure and gets misfiled as one.

A verdict is only a measured result when the comparison was conclusive: adapt.mjs requires zero errored trials, zero unmatched trajectories, and an agreeing summary before it will report a pass or a regression. Confirm that before reading a record as a power problem.

Step 3: Rule out harness and reliability causes

See references/eval-triage.md for the full catalogue. The recurring ones:

• A spec declaring both config: and defaults: is rejected by vally, the job still exits 0, and the PR comment blames "transient infrastructure". Merge them into one defaults: block.
• An errored trial is not automatically a fixture problem — judge-side auth and session.idle failures look identical from the verdict and need harness fixes, not SDK pins.
• expect_tools: [bash] on an advisory question forces a restore or build and turns an answer into a timeout with no quality gain.
• Genuine code-generation stimuli need roughly 360s; a timeout yields empty output, which fails every grader and hides the real quality signal.
• Unmatched trajectories, an errored trial, or a summary that disagrees make the comparison inconclusive: the remaining matched trials are biased, so the record is not a measured null and must not be read as a power or content problem.

Step 4: Verify the fixtures before touching the skill

Run python eng/eval-quality/check_eval_quality.py — it blocks ten defect classes that each already cost a real result here. Then confirm by hand:

• every fixture behaves as its stimulus assumes — a fixture meant to be healthy builds, and one meant to be broken fails for the exact reason the stimulus is about and no other;
• every referenced fixture is in the git index (git ls-files), not merely on disk — .gitignore has silently swallowed committed coverage fixtures;
• a fixture never states the same fact in two places that disagree — a Cobertura report whose declared line-rate, summary totals and <line> elements differ is the canonical case — or the two arms legitimately read different truths.

Step 5: Check whether the eval could ever have passed

The gate has two independent bars, and confusing them is the usual misdiagnosis:

1. Counted trials ≥ 5 (trials = stimuli × runs). Below that the verdict is reported underpowered — never a pass, never a regression.
2. The sign test must reach p ≤ 0.05 over the discordant (non-tie) trials. Ties are not discarded silently; they hold the discordant count down.

So at exactly 5 counted trials a single tie is fatal — it leaves 4 discordant. At 6 counted trials one tie is survivable (5W/1T/0L); at 7, up to two are (5W/2T/0L). A loss is not.

So a positive record with a failing verdict is a power problem, not a content problem. Fix it by adding discriminating stimuli (cross-task evidence) rather than raising runs (repetition only) — except where each stimulus drives an expensive pipeline. Record the reasoning in a comment above defaults:, as tests/dotnet-test/grade-tests/eval.yaml does.

Step 6: Check whether the two arms differ at all

An eval that compares the skill against itself measures judge noise:

• A dormancy guard (expect_activation: false) must not also set constraints.reject_skills. That makes the skilled arm skill-free, i.e. identical to baseline. Across four evals the same guard scored −0.4, +0.4, +0.4 and 0, twice costing a skill its pass.
• A skill with disable-model-invocation: true cannot self-activate, so an eval graded on activation compares two identical arms. Cover it through a consumer skill, or grade the answer content instead, as tests/dotnet-test/filter-syntax/eval.yaml and tests/dotnet-test/platform-detection/eval.yaml do.
• A grader whose config is missing its required key enforces nothing, so the stimulus has one fewer assertion than it appears to.

Step 7: Fix skill content against the losing trial

Only now change the skill. Apply the patterns in references/writing-for-baseline-delta.md; the ones that most often flip a loss:

• Replace reference prose the model already knows with decisions it would otherwise get wrong.
• Add stop-conditions so a strong skill does not over-apply — but do not over-correct into answering more narrowly than the baseline did.
• Scale output structure to input size; a dashboard for an 8-test suite loses to a direct answer.
• Require truthful validation reporting; claiming "Build succeeded" after a failed restore is an automatic loss.
• Verify load-bearing API claims by compiling or probing, not by reading source.
• For cost regressions, gate rare or expensive paths behind references/ reads and size any orchestration to the user's scope.

Step 8: Fix activation

Activation failures are frontmatter and routing failures, not body failures. See references/eval-triage.md. Summary:

Step 9: Re-validate

dotnet run --project eng/skill-validator/src/SkillValidator.csproj -- check --plugin ./plugins/<plugin>
python eng/eval-quality/check_eval_quality.py
./eng/run-skill-evals.sh <plugin> <skill>

Then request the official run by submitting a PR review containing /evaluate (Files changed → Review changes), which binds the run to the reviewed commit. Before declaring a regression on the result, confirm the skill payload actually changed — reruns on byte-identical content have shifted 7W/2T/2L to 4W/5T/2L.

Validation

• For a content fix, a losing trial and the judge's stated reason are quoted in the PR description.
• The failure was classified before any content was edited.
• check_eval_quality.py and skill-validator check both pass.
• Trial count clears the power bar for the observed tie rate, not just the floor of 5.
• Isolated and plugin activation are both reported.
• The PR body records root cause, fix, and validation so the lesson is reusable.

Common Pitfalls

References

• references/writing-for-baseline-delta.md — content patterns that beat the unskilled model
• references/eval-triage.md — symptom, cause and fix catalogue with PR citations
• eng/eval-quality/README.md — the ten structural gate checks and why each exists
• eng/vally-adapter/InvestigatingResults.md — downloading artifacts and reading results.json. This is the current guide; the similarly-named eng/skill-validator/src/docs/InvestigatingResults.md documents the retired skill-validator evaluate schema and does not describe today's results.