Best of Agent Harnesses is a curated directory of agent harnesses, which are runtimes that let AI models act by controlling tools, permissions, context, and saved state around an action loop. It helps people compare harnesses and use related templates, playbooks, and learning resources for building agentic systems. Catalogue entries include agents and other configurations that can query or support the listed harnesses.
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 RyanAlberts/best-of-Agent-Harnesses --skill guardrail-testergit clone --depth 1 https://github.com/RyanAlberts/best-of-Agent-HarnessesWrote 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/ryanalberts/best-of-agent-harnesses/guardrail-tester)<a href="https://agentmods.dev/skills/ryanalberts/best-of-agent-harnesses/guardrail-tester"><img src="https://agentmods.dev/badge/skills/ryanalberts/best-of-agent-harnesses/guardrail-tester/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.
<a href="https://agentmods.dev/skills/ryanalberts/best-of-agent-harnesses/guardrail-tester"><img src="https://agentmods.dev/badge/skills/ryanalberts/best-of-agent-harnesses/guardrail-tester.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00156 | $0.02821 |
| Opus 5.5 | $0.00062 | $0.01128 |
| Sonnet 5.5 | $0.00031 | $0.00564 |
| Haiku 4.5 | $0.00016 | $0.00282 |
Grade C, and why
guardrail-tester scanned grade C with 2 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 6d 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.
Recursive force deletehighDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
hooks block force pushes, rm -rf, secret reads, or downloads piped into a Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
`curl` with the input, a queue), or has other side effects such as writing a log, tell the user The source is not reproduced here
Licensed CC-BY-SA-4.0
The repository is licensed CC-BY-SA-4.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.
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.
- LICENSE.txt 1.0 KB
- README.md 9.6 KB
- references/bypass-forms.md 7.3 KB
- references/harness-rules.md 21 KB
- scripts/battery.json 24 KB
- scripts/claude_rules.py 76 KB runs code
- scripts/harness_rules.py 48 KB runs code
- scripts/hook_runner.py 12 KB runs code
- scripts/safe.py 6.9 KB runs code
- scripts/shell_split.py 23 KB runs code
- scripts/test_guards.py 82 KB runs code
- scripts/transcripts.py 67 KB runs code
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.
- 6d ago First seen · 181 lines · 156 tokens per session scan C b40aa321d323
guardrail-tester is a skill published in the GitHub repository RyanAlberts/best-of-Agent-Harnesses (1,232 stars, last pushed 4d ago), licensed CC-BY-SA-4.0. It adds 156 tokens to every session and 2,821 once invoked, about $0.0006 per session on Opus 5.5. A static security scan graded it C with 2 findings (recursive force delete, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-10.
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Validate, test, and debug regular expressions by executing them against sample inputs. Use when asked to build, verify, or explain a regex pattern.