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/librefang/librefang-registry/oauth-expertnpx skills add librefang/librefang-registry --skill oauth-expertgit clone --depth 1 https://github.com/librefang/librefang-registryWrote 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/librefang/librefang-registry/oauth-expert)<a href="https://agentmods.dev/skills/librefang/librefang-registry/oauth-expert"><img src="https://agentmods.dev/badge/skills/librefang/librefang-registry/oauth-expert.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 | $0.00024 | $0.00744 |
| Opus 5 | $0.00012 | $0.00372 |
| Sonnet 5 | $0.00005 | $0.00149 |
| Haiku 4.5 | $0.00002 | $0.00074 |
Grade A, and why
oauth-expert 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 5d 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.
This is a copy
97% identical to oauth-expert — 3 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 42 lines — stays where its author put it; the contents beside it link to each section on GitHub.
OAuth and OpenID Connect Expert
An identity and access management specialist with deep expertise in OAuth 2.0, OpenID Connect, and token-based authentication architectures. This skill provides guidance for implementing secure authorization flows, token lifecycle management, and identity federation patterns across web applications, mobile apps, SPAs, and machine-to-machine services.
Key Principles
- Always use the Authorization Code flow with PKCE for public clients (SPAs, mobile apps, CLI tools); the implicit flow is deprecated and insecure
- Validate every JWT thoroughly: check the signature algorithm, issuer (iss), audience (aud), expiration (exp), and not-before (nbf) claims before trusting its contents
- Design scopes to represent specific permissions (read:documents, write:orders) rather than broad roles; fine-grained scopes enable least-privilege access
- Store tokens securely: HTTP-only secure cookies for web apps, secure storage APIs for mobile, and encrypted credential stores for server-side services
- Treat refresh tokens as highly sensitive credentials; bind them to the client, rotate on use, and set reasonable absolute expiration times
Techniques
- Implement Authorization Code + PKCE: generate a random code_verifier, derive code_challenge via S256, send the challenge in the authorize request, and send the verifier in the token exchange
- Use Client Credentials flow for server-to-server authentication where no user context is needed; scope the resulting token narrowly
- Configure token refresh with sliding window expiration: issue short-lived access tokens (5-15 minutes) with longer refresh tokens (hours to days), rotating the refresh token on each use
- Implement OIDC by requesting the openid scope; validate the id_token signature and claims, then use the userinfo endpoint for additional profile data
- Set up the Backend-for-Frontend (BFF) pattern for SPAs: the BFF server handles the OAuth flow and stores tokens in HTTP-only cookies, keeping tokens out of JavaScript entirely
- Implement token revocation by calling the revocation endpoint on logout and maintaining a server-side deny list for JWTs that must be invalidated before expiration
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.
- 5d ago First seen · 42 lines · 24 tokens per session scan A bf1ab81b074f
oauth-expert is a skill published in the GitHub repository librefang/librefang-registry (11 stars, last pushed 11d ago), licensed MIT. It adds 24 tokens to every session and 744 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to oauth-expert, differing in 3 lines, and is treated as a copy.
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