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.
npx skills add slowdini/slow-powers --skill evaluating-skillsgit clone --depth 1 https://github.com/slowdini/slow-powersWrote 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.
[](https://agentmods.dev/skills/slowdini/slow-powers/evaluating-skills)<a href="https://agentmods.dev/skills/slowdini/slow-powers/evaluating-skills"><img src="https://agentmods.dev/badge/skills/slowdini/slow-powers/evaluating-skills.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00028 | $0.06958 |
| Opus 5 | $0.00014 | $0.03479 |
| Sonnet 5 | $0.00006 | $0.01392 |
| Haiku 4.5 | $0.00003 | $0.00696 |
Grade A, and why
evaluating-skills 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 7d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 278 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Evaluating skills
Skill development has two phases: drafting (slow-powers:writing-skills) and evaluation (this skill). This skill owns the craft of evaluation — deciding whether a change needs measuring, designing test cases, devising pressure-testing scenarios, writing assertions, and reading results. The mechanics of actually running an eval — building the workspace, staging skills, dispatching subagents, grading, aggregating — are owned by a dedicated tool, eval-magic, which ships as a dependency-less prebuilt binary you invoke as eval-magic. See Running the eval for the hand-off.
Overview
An eval is a structured measurement of whether a skill actually shifts behavior. Each test case is a realistic prompt; each run dispatches a fresh general-purpose subagent twice — once with the skill loaded, once without (or once with the prior version, once with the revised version) — and grades the outputs against assertions. Pass-rate deltas tell you whether the skill is worth shipping or the change is worth landing.
Evals are harness-agnostic: run records use a portable JSON schema so an eval authored on one harness (Claude Code, Codex, OpenCode) can be executed and graded on any other. The runner documents the schema and the per-harness specifics; this skill stays at the level of what makes a good eval.
Two comparison modes
- Mode A — new skill. Compares
with_skillvswithout_skill. Use when validating that a brand-new skill beats baseline behavior with no skill loaded. Best understood as a bundle of removal tests — one case per behavior the skill teaches (see Decompose the skill into behaviors first). - Mode B — revision (the common case). Compares
old_skillvsnew_skill. Use when testing a language change to an existing skill — snapshot the oldSKILL.md, then run both variants against the same prompts. A negative or zero delta is a signal to revert: the new language did not improve behavior.
What ships with it
12 files 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.
- evals/baseline/BASELINE.md 903 B
- evals/baseline/benchmark.json 1.1 KB
- evals/baseline/grading/deterministic-edit-skip__new_skill.json 1.6 KB
- evals/baseline/grading/deterministic-edit-skip__old_skill.json 1.9 KB
- evals/baseline/grading/did-my-revision-help__new_skill.json 1.9 KB
- evals/baseline/grading/did-my-revision-help__old_skill.json 1.8 KB
- evals/baseline/grading/is-new-skill-ready-to-ship__new_skill.json 1.3 KB
- evals/baseline/grading/is-new-skill-ready-to-ship__old_skill.json 1.5 KB
- evals/baseline/NOTES.md 2.3 KB
- evals/evals.json 12 KB
- evals/fixtures/iron-law/candidate-skill.md 451 B
- references/pressure-scenarios.md 8.3 KB
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.
- 7d ago First seen · 278 lines · 28 tokens per session scan A 6c3d4b5e176d
evaluating-skills is a skill published in the GitHub repository slowdini/slow-powers (2 stars, last pushed 24d ago), licensed MIT. It adds 28 tokens to every session and 6,958 once invoked, about $0.0001 per session on Opus 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 2026-08-31.
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