name: skill-eval description: 'Measure whether a skill helps by comparing runs with and without it. Use when: reading skill A/B results or deciding to keep, revise or remove one.' practices:

• measurement-over-assertion
• ab-testing

skill_api_version: 1 hexagonal_role: supporting consumes:

• skill-source-package

produces:

• skill-maintenance-recommendation
• probe-package

context_rel:

• kind: supplier-to

with: skill-builder user-invocable: true metadata: version: "1.0.1" tier: meta dependencies: [] capabilities: ["evaluate_skill_decision","select_skill_measurement","read_skill_ab_results","author_seeded_probe"] effects: ["write_probe_package","dispatch_authorized_trials"] canonical_status: canonical disposition: keep_specialist stability: experimental output_contract: one recommendation (retain, revise, remove or insufficient evidence) with cases, all-attempt denominators, paired outcomes, uncertainty, cost and unknowns

Skill Eval

Answer one named maintenance decision: retain, revise, remove, or insufficient evidence. Choose the measurement that can answer that decision, use the caller's accepted cases and resource envelope, make one scoped recommendation, and stop. A completed evaluation does not require a positive difference.

This is an optional specialist: the selected runner owns execution and bounds, and its native results own the measurements.

Rules that decide the answer

• Count every attempt. Keep failed, crashed, interrupted, blocked, abandoned,

missing and infrastructure-invalid attempts in the all-attempt accounting. A rerun adds an attempt; it never overwrites the one that failed. A run that shared its host with other work still counts for completion and tokens; keep its duration, labeled as measured on a shared host, rather than dropping it. Its timeout is not by itself a skill failure; when timeouts fall unevenly between arms, report them as a possible skill effect, not infrastructure.

• Vary one thing. Equalize instructions, tools, environment, model and

effort across arms apart from the intended variable. If one arm's task prompt repeats the skill's direction, attribute the result to the combined instructions, not the skill alone. When you control launch order, alternate arms run by run, swap which goes first in each pair and rerun a dead run in its own slot; one whole arm and then the other turns load, rate limits and time of day into an apparent skill effect.

• Confirm the skill loaded. Before reading a zero or small delta as no

benefit, check each treatment run for the skill actually being loaded or injected. A run where it never loaded measures routing, not content. When the act depends on a rule kept in a reference, also check that the run opened that file; a run that did not still counts; read its miss as the body's pointer to the reference failing, not the reference's rule, and report how many treatment runs opened the file. The behavioral probe injects only SKILL.md or a prelude, so it cannot answer this. Likewise, a case the no-skill arm already passes nearly in full has no headroom: report no headroom, not no value, and write a harder case (seeding).

• Calibrate the grader. Before trusting scores, confirm the judge or

discriminator passes a response that plainly meets each criterion and fails one that plainly does not. A weak judge can fail correct responses wholesale.

• Small samples are directional. Report uncertainty with every difference.

A difference without it shows neither benefit nor equivalence, and a zero-crossing interval is not equivalence. For two unpaired success rates, give each arm a Wilson interval, the difference with its own interval and Fisher's exact test, not a normal approximation, which breaks at 0/n, n/n and a handful of runs. AgentOps ships no tool for this; the stock calls are scipy.stats.binomtest(k, n).proportion_ci(method="wilson") and scipy.stats.fisher_exact. Beside an inconclusive result, state the runs per arm needed to detect the smallest effect that would change the decision, and return insufficient evidence; running them is a new measurement with its own fixed stop and the caller's authorization, never an extension of this one.

• Fix the stop before running. Do not add trials until the result turns

positive, remove losing observations or relax acceptance.

• Know the noise before cutting. Before trimming or retuning skill text for

a new model, measure how much identical arms differ on the same cases. A cut must clear a bar fixed before the run, above that spread. A static read of the text is not a behavioral result. Saving a result means keeping the completed run; rerunning to save it adds another sample and more spend.

Choose the question

Start from the caller's intended decision, not a mandatory quiz. For a behavioral question, name one observable action (a file written, tool used, criterion rejected); a belief such as “understands validation” needs translation into an action. For coding or memory questions, name unchanged task acceptance and the maintenance choice.

Prefer cases drawn from real use when authorized session history exists: a caller correcting, redoing or overriding the result right after the skill ran is the clearest sign of a miss. Label each case as drawn from use or written from the skill's own text; cases written from the text test what the author expected, not what users hit. With no usable history, say so rather than presenting text-derived cases as representative.

A skill whose result depends on the caller's answers, such as an interview, is not measured by its first turn; never run it where its questions reach a real person. Measure the dialogue as in dialogue skills.

Runners

Select the intersection of the caller's runtime authority, an available adapter and the named question. A runner's presence grants no runtime permission. If no route meets all three, return insufficient evidence with the missing route; do not automatically substitute another runtime or build a replacement runner. Forced SKILL.md injection, natural-request routing and installed-package coding comparisons answer different questions.

When Claude Code is explicitly authorized and its evaluator is available, claude plugin eval <plugin-path> --model <id> is an optional route. It runs the cases in the plugin's eval directory (evals/ by default) with the plugin and, by default (--ablation with-without), without it, scores each response with the case graders (LLM graders use --judge-model, default haiku) and reports the score delta. --runs sets repetitions per case, --max-cost-usd caps spend and --json writes per-run results. The model decides whether to load each skill, so the delta mixes routing with content. By default it also publishes its HTML report (prompts, responses and verdicts) to claude.ai and writes results under the plugin's eval directory: pass --no-publish, and point --output-dir, --json and --report at caller-selected storage. Confirm flags with claude plugin eval --help. In an AgentOps checkout, run the suites as `evals/plugin-eval/README.md` shows and grade with its grade.py: the default Haiku judge failed every criterion of correct validate responses there.

In an AgentOps source checkout, scripts/probe-skill.sh runs small behavioral probes through the Codex adapter (scripts/lib/codex-exec.sh), only when Codex and its isolation support are available and authorized. It injects the exact SKILL.md bytes (or a declared prelude), so it measures the text's effect on one act, not routing or an installed package. Neither runner's result substitutes for the other. Commands, replay limits and headroom classes are in behavioral probes.

The probe runner, evals/, the probe gates and every github.com/boshu2/agentops link in this skill are AgentOps source checkout only; installed skills do not ship them. Elsewhere, use the caller's authorized existing runner if it supports the question and record its identity and limits; with none, report the measurement unsupported rather than installing or starting a replacement.

Procedure

1. Fix the decision and bounds. Name the subject (package, version or

memory update), the cases, the runtime and the time, trial and cost limits, and get the caller's authorization before any live run. Smoke runs, retries and interrupted attempts spend the same limits; a new configuration does not renew them. Token counters are not billing enforcement.

1. Choose the smallest measurement that answers it. Probes for one act,

coding tasks for engineering outcomes, separate later sessions for memory. Keep the deployed model and effort unless the decision is about effort. Keep easy cases as regression and cost controls; never weaken the control arm to manufacture separation.

1. Freeze and calibrate. Fix task, acceptance, package, model, environment

and grader before trials. An executable oracle must accept the intended solution and reject plausible wrong and no-op ones; for judgment, include correct and incomplete cases. A case already used to write or tune the skill is a development case; renaming it does not make it a holdout. A broken or leaked case voids the comparisons it touched. Dry-run a new or changed readout on known input. An A/A gap beyond chance is a harness, labeling or scoring defect to fix before comparing, not noise.

1. Isolate the run. Give trials the selected package and resources; keep

out the operator's home, production tracker, session history, sibling output and solutions. A worktree or a prompt prohibition is not isolation. Capture the launched configuration and final artifacts outside the worker. Report an incompatible adapter rather than building a replacement.

1. Read all attempts from the runner's native results. Wrong identity,

changed acceptance, contamination or ambiguous pairing voids a comparison even when a check passed.

1. Compare only supported facts. Pair by case and repetition. Endpoint

reward, a worker's done claim, an in-workflow validator PASS and independent acceptance are different facts; missing evidence stays unknown. Following an instruction shows adherence, not reduced rework, and a pass far from a failed boundary does not show the boundary is repaired. Coding and memory comparisons follow coding and memory readout.

1. Recommend once and stop. First read a few treatment transcripts, not only

graded outputs: turns spent on steps that do not move the task, and a helper several runs wrote for themselves, are revise targets a passing score hides. A repeated helper is a candidate bundled script under Skill Builder's occurrence rule. A reproduced defect with clean controls supports a provisional narrow repair; general improvement needs a held-out comparison. Do not auto-publish a lesson.

Raw trials and new proof go to caller-selected protected storage outside Git; only sanitized public fixtures cleared for that destination belong in Git (ADR-0016).

Output

Decision: retain | revise | remove | insufficient evidence; scope <skill, version, cases>
Question: <maintenance decision and the measurement chosen>
Setup: <runner, model, effort, grader; what differs between arms>
Attempts: <per arm: assigned, completed, crashed or infra, interrupted, reruns>
Outcomes: <paired by case and repetition; whether the skill loaded in each treatment run>
Uncertainty: <interval and method, or "directional, n=<count>"; runs per arm needed if inconclusive>
Cost: <measured time and cost per arm, or unknown>
Not proven: <confounds, missing coverage, what this measurement cannot show>

Done when the requested measurement has reached its accepted stop, the relevant replay/oracle checks discriminate, missing coverage is explicit, and one recommendation answers the named maintenance decision. Insufficient evidence, an adverse result or an incompatible runtime can complete this evaluation; none counts as demonstrated skill benefit.

References

• Behavioral runner and conventions: `scripts/probe-skill.sh`, `evals/skill-probes/README.md`, seeding.
• Plugin A/B suites and grader: `evals/plugin-eval/README.md`.
• Behavioral verdicts and non-verdict incidents: `LEDGER.md`, `RUNBOOK.md`.
• Existing coverage and headroom gates: `check-skill-probe-coverage.sh`, `check-skill-probe-headroom.sh`.
• Evidence and overclaim limits: ADR-0011, ADR-0016 and `RPI traversal`.