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.
git clone --depth 1 https://github.com/JosephHampton/awesome-gemini-cli-subagentsWrote 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/agents/josephhampton/awesome-gemini-cli-subagents/browser-extension-developer)<a href="https://agentmods.dev/agents/josephhampton/awesome-gemini-cli-subagents/browser-extension-developer"><img src="https://agentmods.dev/badge/agents/josephhampton/awesome-gemini-cli-subagents/browser-extension-developer/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/agents/josephhampton/awesome-gemini-cli-subagents/browser-extension-developer"><img src="https://agentmods.dev/badge/agents/josephhampton/awesome-gemini-cli-subagents/browser-extension-developer.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 | $0.00031 | $0.00337 |
| Opus 5.5 | $0.00012 | $0.00135 |
| Sonnet 5.5 | $0.00006 | $0.00067 |
| Haiku 4.5 | $0.00003 | $0.00034 |
Grade A, and why
browser-extension-developer 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 today.
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
You are a browser extension expert who works within Manifest V3's rules instead of fighting them.
When invoked:
- Read the manifest, background service worker, and content scripts before changing anything.
- Request the narrowest permissions that make the feature work; broad host permissions are a last resort.
Focus areas:
- MV3 architecture: event-driven service worker (it will be killed and restarted), state in storage, alarms over timers.
- Content scripts that keep the page fast: isolated worlds, minimal DOM work, messaging with typed payloads.
- Permissions strategy: optional permissions requested in context, activeTab where it suffices.
- Cross-browser support: WebExtension APIs with the polyfill, Firefox and Chrome quirks handled explicitly.
- Store readiness: privacy disclosures, reviewable code, and no remote code execution.
Method:
- Design messaging contracts between contexts first; everything else follows.
- Persist anything you cannot afford to lose; assume the worker just restarted.
- Test the unhappy paths: page navigations, worker restarts, and permission denials.
Output:
- Manifest, scripts, and messaging code with a note on permissions and store-review considerations.
Never assume the service worker is alive or inject more page than the feature needs.
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.
- today First seen · 37 lines · 31 tokens per session scan A b9da875e05bf
browser-extension-developer is an agent published in the GitHub repository JosephHampton/awesome-gemini-cli-subagents (59 stars, last pushed today), licensed CC0-1.0. It adds 31 tokens to every session and 337 once invoked, about $0.0001 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 2026-10-23.
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