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-pluginsgit 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-plugins)<a href="https://agentmods.dev/skills/bobmatnyc/claude-mpm-skills/better-auth-plugins"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/better-auth-plugins/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-plugins"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/better-auth-plugins.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium MCP Rug Pull · line 49 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 53 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
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 | $0.00041 | $0.00467 |
| Opus 5 | $0.00020 | $0.00234 |
| Sonnet 5 | $0.00008 | $0.00093 |
| Haiku 4.5 | $0.00004 | $0.00047 |
Grade A, and why
better-auth-plugins 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 9d 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 Plugins
Goals
- Add server plugins to extend auth features.
- Add client plugins for matching client methods.
- Apply schema changes when plugins add tables.
Quick start
- Import the plugin from
better-auth/pluginsand add it toplugins. - Run migrations (
generateormigrate) when required. - Add the client plugin from
better-auth/client/plugins.
Example: Two-factor authentication
import { betterAuth } from "better-auth";
import { twoFactor } from "better-auth/plugins";
export const auth = betterAuth({
plugins: [twoFactor()],
});
import { createAuthClient } from "better-auth/client";
import { twoFactorClient } from "better-auth/client/plugins";
export const authClient = createAuthClient({
plugins: [twoFactorClient({ twoFactorPage: "/two-factor" })],
});
Migration reminder
Run the CLI when a plugin adds tables:
npx @better-auth/cli generate
npx @better-auth/cli migrate
Guardrails
- Add server and client plugins together to keep APIs aligned.
- Keep
nextCookies(if used) last in the server plugin list. - Review plugin docs for required schema and env variables.
References
toolchains/platforms/auth/better-auth/better-auth-plugins/references/plugins-index.md
What ships with it
2 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.
- 9d ago First seen · 63 lines · 41 tokens per session scan A d0849927001e
better-auth-plugins is a skill published in the GitHub repository bobmatnyc/claude-mpm-skills (75 stars, last pushed 1mo ago), licensed MIT. It adds 41 tokens to every session and 467 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 2026-09-03.
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