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 idempotency-handlinggit 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/idempotency-handling)<a href="https://agentmods.dev/skills/aj-geddes/useful-ai-prompts/idempotency-handling"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/idempotency-handling/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/idempotency-handling"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/idempotency-handling.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 | $0.00039 | $0.00605 |
| Opus 5 | $0.00019 | $0.00302 |
| Sonnet 5 | $0.00008 | $0.00121 |
| Haiku 4.5 | $0.00004 | $0.00060 |
Grade A, and why
idempotency-handling scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Idempotency Handling
Table of Contents
Overview
Implement idempotency to ensure operations produce the same result regardless of how many times they're executed.
When to Use
- Payment processing
- API endpoints with retries
- Webhooks and callbacks
- Message queue consumers
- Distributed transactions
- Bank transfers
- Order creation
- Email sending
- Resource creation
Quick Start
Minimal working example:
import express from "express";
import Redis from "ioredis";
import crypto from "crypto";
interface IdempotentRequest {
key: string;
status: "processing" | "completed" | "failed";
response?: any;
error?: string;
createdAt: number;
completedAt?: number;
}
class IdempotencyService {
private redis: Redis;
private ttl = 86400; // 24 hours
constructor(redisUrl: string) {
this.redis = new Redis(redisUrl);
}
async getRequest(key: string): Promise<IdempotentRequest | null> {
const data = await this.redis.get(`idempotency:${key}`);
return data ? JSON.parse(data) : null;
}
// ... (see reference guides for full implementation)
Reference Guides
Detailed implementations in the references/ directory:
| Guide | Contents |
|---|---|
| Express Idempotency Middleware | Express Idempotency Middleware |
| Database-Based Idempotency | Database-Based Idempotency |
| Stripe-Style Idempotency | Stripe-Style Idempotency |
| Message Queue Idempotency | Message Queue Idempotency |
Best Practices
✅ DO
- Require idempotency keys for mutations
- Store request and response together
- Set appropriate TTL for idempotency records
- Validate request body matches stored request
- Handle concurrent requests gracefully
- Return same response for duplicate requests
- Clean up old idempotency records
- Use database constraints for atomicity
What ships with it
6 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 · 100 lines · 39 tokens per session scan A 5ed3ee0194ee
idempotency-handling is a skill published in the GitHub repository aj-geddes/useful-ai-prompts (338 stars, last pushed 6mo ago), licensed MIT. It adds 39 tokens to every session and 605 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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