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 brsbl/moss-skills --skill moss-frontmattergit clone --depth 1 https://github.com/brsbl/moss-skillsWrote 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/brsbl/moss-skills/moss-frontmatter)<a href="https://agentmods.dev/skills/brsbl/moss-skills/moss-frontmatter"><img src="https://agentmods.dev/badge/skills/brsbl/moss-skills/moss-frontmatter/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/brsbl/moss-skills/moss-frontmatter"><img src="https://agentmods.dev/badge/skills/brsbl/moss-skills/moss-frontmatter.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 | $0.00034 | $0.00407 |
| Opus 5 | $0.00017 | $0.00204 |
| Sonnet 5 | $0.00007 | $0.00081 |
| Haiku 4.5 | $0.00003 | $0.00041 |
Grade A, and why
moss-frontmatter 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
Moss Frontmatter
Frontmatter is an optional top-level YAML mapping before the note's H1.
---
status: active
tags:
- project
people:
- jane
---
# Note Title
Authoring Contract
- Use frontmatter for structured fields that help search, filtering, grouping, or retrieval.
- Prefer scalars and lists of strings. Moss parses nested arrays and objects but displays them read-only; preserve them unless the task explicitly requests a filesystem edit to that structure.
typeandstatusare workspace vocabularies, not fixed enums. Reuse values already present in the workspace when possible.- Common fields are
type,people,description,tags, andstatus; unknown fields are valid and must be preserved. - For workspace notes under
~/Moss/Notes/, preserve existingcreated_dateand let Moss set it for new notes. Do not invent or overwrite it. - The note title comes from the leading H1, not a
titlefield. - Do not duplicate metadata as body headings or bold labels.
- Omit frontmatter when the note has no useful metadata.
Editing And Recovery
Filesystem writers may edit any field the task explicitly targets, including a nested value, while preserving unrelated keys. The Moss Properties UI edits supported scalar/list fields and treats nested values as read-only.
Keep YAML valid and retain the top-level mapping. If existing frontmatter is malformed, preserve it unless the user asks for repair; Moss retains malformed YAML but cannot edit it through Properties.
Final Check
- Frontmatter is the first block and closes before the H1.
- YAML is a top-level mapping.
- Unknown and unrelated fields remain intact.
- Workspace-managed
created_datewas not invented or overwritten.
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.
- 10d ago First seen · 45 lines · 34 tokens per session scan A 37d07dfce291
moss-frontmatter is a skill published in the GitHub repository brsbl/moss-skills (11 stars, last pushed 16d ago), licensed MIT. It adds 34 tokens to every session and 407 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 2026-08-31.
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