skill-eval

skill-eval is a skill for Claude Code from aiocean/claude-plugins. It costs 98 tokens per session (1,034 once invoked), scanned A, original, MIT.

A test runner for checking whether an agent add-on triggers on the right prompts and improves results. It runs prompts with, without, or against another version of the add-on and scores the outputs.

In plain words
What is it for?
Use it to evaluate a plugin before release, compare old and new versions, measure trigger behavior, and re-grade runs after changing the checks or scoring rules.
Why use it?
It provides a repeatable way to catch skills that activate on unrelated requests or fail to improve an agent's work. It also supports checking whether a change is better than an earlier version.

Skill for Claude Code

Written for Claude Code: installed under .claude/. Also seen: mentions CLAUDE.md.

Good fit Use it to evaluate a plugin before release, compare old and new versions, measure trigger behavior, and re-grade runs after changing the checks or scoring rules.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/aiocean/claude-plugins/skill-eval
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add aiocean/claude-plugins --skill skill-eval
Clone the repo
git clone --depth 1 https://github.com/aiocean/claude-plugins

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for skill-eval

README.md
[![agentmods](https://agentmods.dev/badge/skills/aiocean/claude-plugins/skill-eval/github.svg)](https://agentmods.dev/skills/aiocean/claude-plugins/skill-eval)
Your own site
<a href="https://agentmods.dev/skills/aiocean/claude-plugins/skill-eval"><img src="https://agentmods.dev/badge/skills/aiocean/claude-plugins/skill-eval/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for skill-eval

Your own site · 80×15
<a href="https://agentmods.dev/skills/aiocean/claude-plugins/skill-eval"><img src="https://agentmods.dev/badge/skills/aiocean/claude-plugins/skill-eval.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 98 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,034 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00098 $0.01034
Opus 5.5 $0.00039 $0.00414
Sonnet 5.5 $0.00020 $0.00207
Haiku 4.5 $0.00010 $0.00103

Measured 4d ago against content hash 8780c777b9c4, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

skill-eval scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (skill-eval.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/skill-eval/SKILL.md · 68 lines

How it starts

The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.

skill-eval

Runs headless claude -p agents on a suite of prompts, once per arm, then scores each run.

Arm What the agent sees
with plugins/<plugin> from the working tree
without no plugin
against plugins/<plugin> at --against <git-ref>, for old-vs-new comparisons

Every run uses a fresh temp workdir outside the repo with --setting-sources project,local --strict-mcp-config. User plugins, hooks, MCP servers and the global CLAUDE.md are not loaded, so the only non-built-in skill an arm can see is the one under test. Trigger rates are therefore measured without competition from other installed skills.

Run

EVAL=.claude/skills/skill-eval/skill-eval.py
python3 $EVAL run evals/<plugin>/<suite>.json --model sonnet --reps 3 --budget 1
python3 $EVAL run evals/<plugin>/<suite>.json --arms with,against --against HEAD   # did my uncommitted edit help?
python3 $EVAL grade evals/<plugin>/runs/<run-id>                                   # re-grade after editing checks/rubric

run --help lists every flag. Output goes to evals/<plugin>/runs/<suite>-<timestamp>/ (gitignored): summary.md holds the table, and each <case>/<arm>-<rep>/ holds transcript.jsonl, run.json (tool calls, cost, turns, final reply), grading.json and work/ (files after the run).

Each run is a paid model call. Run 1 rep on one --case first, read its transcript, then scale up.

Suite format

evals/<plugin>/<suite>.json. Example: evals/aio-anti-slop/prose.json.

{
  "plugin": "aio-anti-slop", "skill": "aio-anti-slop",
  "permission_mode": "acceptEdits", "allowed_tools": ["Bash"],
  "cases": [{
    "id": "readme-robotic",
    "prompt": "Our README.md sounds robotic ...",
    "files": {"README.md": "seed content"},
    "trigger": true,
    "checks": [{"desc": "install command kept", "file": "README.md", "regex": "bun add tinyq"},
               {"desc": "answers O(log n)", "output": true, "not_regex": "..."}],
    "rubric": ["README.md adds no new factual claims"]
  }]
}

Read the full file on GitHub · 68 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 68 lines · 98 tokens per session scan A 8780c777b9c4

Subscribe to this mod's changes

skill-eval is a skill published in the GitHub repository aiocean/claude-plugins (4 stars, last pushed 2d ago), licensed MIT. It adds 98 tokens to every session and 1,034 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-26.