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 abel30567/fermi-mcp --skill totp-oauthgit clone --depth 1 https://github.com/abel30567/fermi-mcpWrote 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/abel30567/fermi-mcp/totp-oauth)<a href="https://agentmods.dev/skills/abel30567/fermi-mcp/totp-oauth"><img src="https://agentmods.dev/badge/skills/abel30567/fermi-mcp/totp-oauth/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/abel30567/fermi-mcp/totp-oauth"><img src="https://agentmods.dev/badge/skills/abel30567/fermi-mcp/totp-oauth.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 | $0.00038 | $0.00468 |
| Opus 5.5 | $0.00015 | $0.00187 |
| Sonnet 5.5 | $0.00008 | $0.00094 |
| Haiku 4.5 | $0.00004 | $0.00047 |
Grade A, and why
totp-oauth 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.
What it actually says
Fermi OAuth 2.0 + TOTP owner auth
Built in PR #5 (issue #4); provider refactored onto
@cloudflare/workers-oauth-provider (issue #7). Protects the MCP endpoints and
private R2-hosted apps.
Flow
- MCP client hits
/mcpor/sse; with auth enabled it is redirected into the OAuth flow at/oauth/authorize(PKCE required, plain PKCE disallowed). - The authorize page asks for the owner secret + a 6-digit TOTP code
(Google Authenticator, seeded from
{{secret:FERMI_TOTP_SECRET}}). - On success the provider issues tokens via
/oauth/token; client registration is at/oauth/register(scope:mcp). - Private apps under
/apps/*use the same owner+TOTP login at/apps/_login; the session cookie lasts 24h./apps/public/*skips auth entirely.
Rollback flag
FERMI_AUTH_ENABLED (worker var). 'true' routes everything through the
OAuthProvider; any other value serves the default handler with no auth. If auth
breaks (e.g. client Zod validation of redirect_uris), set it to 'false',
redeploy, and debug offline.
Gotchas
- TOTP codes are all-numeric — a historical regex bug rejected valid codes (fixed in #9); validate with a numeric-aware pattern.
- The owner secret and TOTP seed live in the secrets store; never hardcode them.
- Token lifetimes follow the provider defaults; the apps session cookie (24h) is independent of MCP tokens.
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 · 35 lines · 38 tokens per session scan A 81daccd09f1b
totp-oauth is a skill published in the GitHub repository abel30567/fermi-mcp (1 stars, last pushed 4d ago), licensed MIT. It adds 38 tokens to every session and 468 once invoked, about $0.0002 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 2026-08-31.
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