Borrowing it
Nothing to install: this file belongs to noontide-co/mainbranch. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/noontide-co/mainbranch/main/.claude/skills/mb-skill-concept/SKILL.mdgit clone --depth 1 https://github.com/noontide-co/mainbranchWrote 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/noontide-co/mainbranch/mb-skill-concept)<a href="https://agentmods.dev/skills/noontide-co/mainbranch/mb-skill-concept"><img src="https://agentmods.dev/badge/skills/noontide-co/mainbranch/mb-skill-concept/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/noontide-co/mainbranch/mb-skill-concept"><img src="https://agentmods.dev/badge/skills/noontide-co/mainbranch/mb-skill-concept.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 | $0.00045 | $0.00427 |
| Opus 5 | $0.00023 | $0.00214 |
| Sonnet 5 | $0.00009 | $0.00085 |
| Haiku 4.5 | $0.00005 | $0.00043 |
Grade A, and why
mb-skill-concept 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 10d 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.
What it actually says
skill-concept
A composable skill for generating concept variations. /mb-site calls this after the brief is locked, before the first publish.
Inputs
- The locked brief (path provided in the user message)
- Reference URLs (taste anchors, not templates)
- Conversion endpoint config (
.mainbranch/conversion.json)
Outputs
- N localhost-runnable HTML variations, each in its own subdir of the project repo (e.g.,
concepts/v1/,concepts/v2/) - A short comparison summary for the operator: hero artifact, palette, voice variant for each
- Operator picks one; that variation is promoted to the project root
Flow
- Spawn N foreground subagents (default 2). Each gets the same brief + reference URLs but is asked to make different decisions.
- Each subagent writes its variation. Foreground only — background writes are known to silently fail.
- Validate each variation: footer present, OG.svg under 1200×630, no AI tells in the copy.
- Render preview.
python3 -m http.serverfrom each subdir; open in browser. - Operator picks. One concept → promoted to repo root; others archived under
concepts/.
Foreground rule
Subagents MUST be foreground. The known background-subagent file-write bug means files appear written but don't persist. Foreground only. See references/concept-variations.md for the spawn pattern.
Cross-references
What ships with it
3 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.
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.
- 10d ago First seen · 41 lines · 45 tokens per session scan A b42e99104ca0
mb-skill-concept is a skill published in the GitHub repository noontide-co/mainbranch (39 stars, last pushed 26d ago), licensed MIT. It adds 45 tokens to every session and 427 once invoked, about $0.0002 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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