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 cubxxw/agent-kit --skill boundary-demogit clone --depth 1 https://github.com/cubxxw/agent-kitWrote 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/cubxxw/agent-kit/boundary-demo)<a href="https://agentmods.dev/skills/cubxxw/agent-kit/boundary-demo"><img src="https://agentmods.dev/badge/skills/cubxxw/agent-kit/boundary-demo/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/cubxxw/agent-kit/boundary-demo"><img src="https://agentmods.dev/badge/skills/cubxxw/agent-kit/boundary-demo.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 | $0.00066 | $0.00904 |
| Opus 5.5 | $0.00026 | $0.00362 |
| Sonnet 5.5 | $0.00013 | $0.00181 |
| Haiku 4.5 | $0.00007 | $0.00090 |
Grade A, and why
boundary-demo 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 1mo 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 — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Boundary Demo
Build the smallest probe that can change one decision. The deliverable is evidence, not a miniature product.
Start with one decision contract
Before implementation, write down:
- one question with at least two plausible answers;
- the evidence that would change the decision;
- the smallest observable failure;
- a timebox and stop rule;
- what is explicitly out of scope.
If these cannot be stated, ask one concise question. Do not expand into a full product specification. Read references/choosing-and-scoping.md when the right probe or medium is unclear.
Choose exactly one mode
- Boundary: contracts, ownership, external services, failures, retries, or side effects. Default integrations to deterministic fake or read-only adapters.
- Logic: state machines, data shapes, policies, or transitions. Keep the runner independent of the UI.
- Taste: interaction or information hierarchy is the uncertainty. Compare two or three materially different variants against the same cases; read references/taste-comparison.md.
Do not run all modes by default. Choose the medium after the mode:
- Prefer Streamlit for Python, data, LLM, state, trace, and human-review probes.
- Prefer a CLI when the question is pure state or business logic and a browser adds no evidence.
- Use an existing Web surface when DOM, CSS, responsive behavior, browser events, or page context is itself under test.
Build an observable probe
Make input, relevant state before and after, trace, output, and failure visible. Seed at least one normal, one edge, and one failure case. Keep four evidence classes separate:
- observed fact;
- automated verdict;
- human choice;
- AI hypothesis.
An automated pass never promotes a discovery case to regression or Gold. Only the user can confirm the expected behavior or taste choice.
For a new Streamlit probe, initialize the bundled example:
python <SKILL_DIR>/scripts/init_demo.py <TARGET_DIR> \
--question "<ONE DECISION QUESTION>"
What ships with it
24 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.
- agents/openai.yaml 228 B
- assets/streamlit-boundary-demo/.gitignore 69 B
- assets/streamlit-boundary-demo/.streamlit/config.toml 48 B
- assets/streamlit-boundary-demo/boundary_demo/__init__.py 51 B runs code
- assets/streamlit-boundary-demo/boundary_demo/adapters.py 1.1 KB runs code
- assets/streamlit-boundary-demo/boundary_demo/cases.py 2.4 KB runs code
- assets/streamlit-boundary-demo/boundary_demo/contracts.py 950 B runs code
- assets/streamlit-boundary-demo/boundary_demo/evaluation.py 2.0 KB runs code
- assets/streamlit-boundary-demo/boundary_demo/runner.py 4.7 KB runs code
- assets/streamlit-boundary-demo/cases/edge.json 997 B
- assets/streamlit-boundary-demo/cases/failure.json 973 B
- assets/streamlit-boundary-demo/cases/normal.json 976 B
- assets/streamlit-boundary-demo/decision.md 479 B
- assets/streamlit-boundary-demo/experiment.md 1.2 KB
- assets/streamlit-boundary-demo/pyproject.toml 308 B
- assets/streamlit-boundary-demo/streamlit_app.py 4.3 KB runs code
- assets/streamlit-boundary-demo/tests/test_app.py 1.6 KB runs code
- assets/streamlit-boundary-demo/tests/test_cases.py 1.0 KB runs code
- assets/streamlit-boundary-demo/tests/test_runner.py 1.8 KB runs code
- references/cases-and-review.md 3.2 KB
- references/choosing-and-scoping.md 1.9 KB
- references/streamlit-runtime.md 2.8 KB
- references/taste-comparison.md 1.4 KB
- scripts/init_demo.py 3.1 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.
- 1mo ago First seen · 105 lines · 66 tokens per session scan A 656d767c49e5
boundary-demo is a skill published in the GitHub repository cubxxw/agent-kit (2 stars, last pushed 4d ago), licensed MIT. It adds 66 tokens to every session and 904 once invoked, about $0.0003 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 2026-09-08.
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