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/acaprino/daodan/firefox-extension-devnpx skills add acaprino/daodan --skill firefox-extension-devgit clone --depth 1 https://github.com/acaprino/daodanWrote 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/acaprino/daodan/firefox-extension-dev)<a href="https://agentmods.dev/skills/acaprino/daodan/firefox-extension-dev"><img src="https://agentmods.dev/badge/skills/acaprino/daodan/firefox-extension-dev.svg" alt="Measured on agentmods" 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 | $0.00044 | $0.00247 |
| Opus 5 | $0.00022 | $0.00123 |
| Sonnet 5 | $0.00009 | $0.00049 |
| Haiku 4.5 | $0.00004 | $0.00025 |
Grade A, and why
firefox-extension-dev 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 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.
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
Firefox Extension Development References
This skill provides reference files for the firefox-extension-dev agent. The agent handles all active development work (scaffolding, coding, debugging, publishing). These reference files serve as its knowledge base.
Reference Files
references/browser-api-reference.md- Complete list of all 51 browser.* APIs with methods, events, and permissionsreferences/manifest-schema.md- Full manifest.json key reference with MV2/MV3 examplesreferences/amo-publishing.md- AMO publishing checklist, review policies, CSP, security best practices, i18nreferences/mdn-api-urls.md- Direct MDN URL index for all browser.* APIs, manifest keys, and Extension Workshop resourcesreferences/best-practices.md- Best practices, pitfalls, and anti-patterns: JS patterns, Workers, sessions, startup, security, performance, cross-browser
What ships with it
5 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.
- 6d ago First seen · 19 lines · 44 tokens per session scan A 9f52581381b9
firefox-extension-dev is a skill published in the GitHub repository acaprino/daodan (8 stars, last pushed yesterday), licensed MIT. It adds 44 tokens to every session and 247 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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