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 agentmods add skills/fastxyz/skill-optimizer/skill-optimizernpx skills add fastxyz/skill-optimizer --skill skill-optimizergit clone --depth 1 https://github.com/fastxyz/skill-optimizerWhat 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 | $0.00052 | $0.02349 |
| Opus 5 | $0.00026 | $0.01175 |
| Sonnet 5 | $0.00010 | $0.00470 |
| Haiku 4.5 | $0.00005 | $0.00235 |
Grade A, and why
skill-optimizer 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 3d 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 — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.
skill-optimizer
skill-optimizer is an eval workbench for agent skills. It runs a model in an isolated Docker /work directory, provides skills/references as normal workspace files, captures an agent trace, and grades deterministic local outcomes.
Use this skill as the source of truth for authoring eval suites in this repo. Detailed schema and patterns are in references/workbench.md.
Core Model
- A case is one user-like task plus one or more deterministic graders.
- A suite is a set of cases and OpenRouter models to run as a matrix.
referencesare copied into/workbefore the agent starts; this is where eval skills live.- The agent phase sees
/workonly. It cannot see/case,/results, graders, hidden answers, or hidden metadata. - Cases can define
mcpServers; these are exposed through a workbenchmcpcommand during the agent phase. - Graders run after the agent with
/case,/work, and/resultsmounted. trace.jsonlis the debugging source for what the agent saw, said, and did.
Commands
| Goal | Command |
|---|---|
| Install deps | npm install |
| Build CLI | npm run build |
| Run one case | npx tsx src/cli.ts run-case <case.yml> |
| Run one case across models | npx tsx src/cli.ts run-case <case.yml> --models openrouter/google/gemini-2.5-flash,openrouter/openai/gpt-5.4 |
| Run a suite | npx tsx src/cli.ts run-suite <suite.yml> |
| CLI help | npx tsx src/cli.ts --help |
Rules:
- Use only
openrouter/...model refs. OPENROUTER_API_KEYis required for real model runs.run-suiteusesmodels:fromsuite.yml; it has no model override flag.run-casecan use its casemodel:or--model/--models.- Docker image default is
skill-optimizer-workbench:local.
Install This Skill
This repository ships one canonical skill at skills/skill-optimizer/SKILL.md plus plugin metadata for Claude Code, OpenCode, Codex, Cursor, and Gemini.
Install the skill for common agents with:
npx skills add fastxyz/skill-optimizer --skill skill-optimizer -a claude-code -a opencode -a codex -a cursor
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.
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.
- 3d ago First seen · 211 lines · 52 tokens per session scan A 8875c9505df1
skill-optimizer is a skill published in the GitHub repository fastxyz/skill-optimizer (77 stars, last pushed 3mo ago), licensed MIT. It adds 52 tokens to every session and 2,349 once invoked, about $0.0003 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 2026-08-30.
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