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 aj-geddes/useful-ai-prompts --skill api-authenticationgit clone --depth 1 https://github.com/aj-geddes/useful-ai-promptsWrote 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/aj-geddes/useful-ai-prompts/api-authentication)<a href="https://agentmods.dev/skills/aj-geddes/useful-ai-prompts/api-authentication"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/api-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/aj-geddes/useful-ai-prompts/api-authentication"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/api-authentication.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk 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 | $0.00038 | $0.00629 |
| Opus 5 | $0.00019 | $0.00315 |
| Sonnet 5 | $0.00008 | $0.00126 |
| Haiku 4.5 | $0.00004 | $0.00063 |
Grade A, and why
api-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 10d 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.
How it starts
The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API Authentication
Table of Contents
Overview
Implement comprehensive authentication strategies for APIs including JWT tokens, OAuth 2.0, API keys, and session management with proper security practices.
When to Use
- Securing API endpoints
- Implementing user login/logout flows
- Managing access tokens and refresh tokens
- Integrating OAuth 2.0 providers
- Protecting sensitive data
- Implementing API key authentication
Quick Start
Minimal working example:
// Node.js JWT Implementation
const express = require('express');
const jwt = require('jsonwebtoken');
const bcrypt = require('bcrypt');
const app = express();
const SECRET_KEY = process.env.JWT_SECRET || 'your-secret-key';
const REFRESH_SECRET = process.env.REFRESH_SECRET || 'your-refresh-secret';
// User login endpoint
app.post('/api/auth/login', async (req, res) => {
try {
const { email, password } = req.body;
// Find user in database
const user = await User.findOne({ email });
if (!user) {
return res.status(401).json({ error: 'Invalid credentials' });
}
// Verify password
const isValid = await bcrypt.compare(password, user.password);
if (!isValid) {
return res.status(401).json({ error: 'Invalid credentials' });
}
// ... (see reference guides for full implementation)
Reference Guides
Detailed implementations in the references/ directory:
| Guide | Contents |
|---|---|
| JWT Authentication | JWT Authentication |
| OAuth 2.0 Implementation | OAuth 2.0 Implementation |
| API Key Authentication | API Key Authentication |
| Python Authentication Implementation | Python Authentication Implementation |
What ships with it
5 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.
- 10d ago First seen · 102 lines · 38 tokens per session scan A d0538a10cc94
api-authentication is a skill published in the GitHub repository aj-geddes/useful-ai-prompts (336 stars, last pushed 6mo ago), licensed MIT. It adds 38 tokens to every session and 629 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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