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 bobmatnyc/claude-mpm-skills --skill better-auth-authenticationgit clone --depth 1 https://github.com/bobmatnyc/claude-mpm-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/bobmatnyc/claude-mpm-skills/better-auth-authentication)<a href="https://agentmods.dev/skills/bobmatnyc/claude-mpm-skills/better-auth-authentication"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/better-auth-authentication/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/bobmatnyc/claude-mpm-skills/better-auth-authentication"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/better-auth-authentication.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 | $0.00037 | $0.00589 |
| Opus 5 | $0.00018 | $0.00295 |
| Sonnet 5 | $0.00007 | $0.00118 |
| Haiku 4.5 | $0.00004 | $0.00059 |
Grade A, and why
better-auth-authentication 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 11d 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
Better Auth Authentication
Goals
- Enable email/password authentication and social providers.
- Implement sign-up, sign-in, sign-out, and verification flows.
- Handle redirects and errors consistently.
Quick start
- Enable
emailAndPasswordand configuresocialProviders. - Create a client with
createAuthClient. - Use
signUp.email,signIn.email,signIn.social, andsignOuton the client.
import { betterAuth } from "better-auth";
export const auth = betterAuth({
emailAndPassword: { enabled: true },
socialProviders: {
github: {
clientId: process.env.GITHUB_CLIENT_ID as string,
clientSecret: process.env.GITHUB_CLIENT_SECRET as string,
},
},
});
import { createAuthClient } from "better-auth/client";
const authClient = createAuthClient();
await authClient.signUp.email({
email,
password,
name,
});
await authClient.signIn.email({
email,
password,
callbackURL: "/dashboard",
});
await authClient.signIn.social({
provider: "github",
callbackURL: "/dashboard",
});
await authClient.signOut();
Email verification
- Provide
emailVerification.sendVerificationEmailto send the verification link. - Use
emailAndPassword.requireEmailVerificationto enforce verification before sign-in.
Social providers
- Configure providers in
socialProviderswith provider-specific credentials. - Use
signIn.socialto start OAuth flows. - Pass
callbackURL,errorCallbackURL, andnewUserCallbackURLfor redirects.
Guardrails
- Call client methods from the client only.
- Keep secrets in server-only env variables.
- Use
rememberMeto control persistent sessions on email/password sign-in.
References
toolchains/platforms/auth/better-auth/better-auth-authentication/references/email-password.mdtoolchains/platforms/auth/better-auth/better-auth-authentication/references/providers.md
What ships with it
3 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.
- 11d ago First seen · 83 lines · 37 tokens per session scan A 34728b24915e
better-auth-authentication is a skill published in the GitHub repository bobmatnyc/claude-mpm-skills (74 stars, last pushed 1mo ago), licensed MIT. It adds 37 tokens to every session and 589 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 2026-08-30.
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