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 rrezartprebreza/spring-boot-skills --skill idempotency-patternsgit clone --depth 1 https://github.com/rrezartprebreza/spring-boot-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/rrezartprebreza/spring-boot-skills/idempotency-patterns)<a href="https://agentmods.dev/skills/rrezartprebreza/spring-boot-skills/idempotency-patterns"><img src="https://agentmods.dev/badge/skills/rrezartprebreza/spring-boot-skills/idempotency-patterns/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/rrezartprebreza/spring-boot-skills/idempotency-patterns"><img src="https://agentmods.dev/badge/skills/rrezartprebreza/spring-boot-skills/idempotency-patterns.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00046 | $0.00766 |
| Opus 5.5 | $0.00018 | $0.00306 |
| Sonnet 5.5 | $0.00009 | $0.00153 |
| Haiku 4.5 | $0.00005 | $0.00077 |
Grade A, and why
idempotency-patterns 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 1mo 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 — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Idempotency Patterns
Spring Boot 3 baseline
The examples use Java 17 and Jakarta APIs supported by this Boot version. Keep dependencies managed by the project's Boot BOM.
Define the contract
Identify the authenticated tenant/principal, operation, idempotency key, canonical request hash, retention window and replayable result. Scope uniqueness by principal/tenant and operation; a raw client key must never allow reading another user's result. Authenticate and authorize before both initial execution and replay. Bound key length and stored response size. Document what same-key/different-payload and still-in-progress requests return.
Database-local effects
For PostgreSQL, the schema and claim example uses a composite primary key and INSERT ON CONFLICT DO NOTHING RETURNING. In a single database transaction: claim the key, apply the business write, store the resulting status/body/selected headers, then commit. Roll back the claim with the business mutation on failure.
If the insert returns no row, load the existing result in a subsequent statement under READ COMMITTED, compare the canonical hash and replay only when it matches. A concurrent insert waits on the uniqueness constraint; bound lock waits and return a documented retryable outcome on timeout. With snapshot isolation, serialization failures require retrying the whole transaction. Do not catch a unique-constraint violation and continue in an already-aborted transaction.
A result row and business write must use the same transaction manager and database. Return the stored result rather than reconstructing it from mutable current entity state. Keep replay headers allowlisted; do not persist cookies, bearer tokens or hop-by-hop headers.
External effects and messages
A database transaction cannot atomically include an HTTP payment or email. Write an outbox record with the business mutation and let a retryable worker perform the external effect using the provider's idempotency support. Reconcile uncertain outcomes before retrying irreversible effects. For messages, record a unique consumer/event pair and apply the projection in one transaction; acknowledge only after commit. Retry failed transactions and route poison messages deliberately.
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.
- 1mo ago First seen · 70 lines · 46 tokens per session scan A b7d4e0c79536
idempotency-patterns is a skill published in the GitHub repository rrezartprebreza/spring-boot-skills (324 stars, last pushed 2d ago), licensed MIT. It adds 46 tokens to every session and 766 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-08.
Other skills, from other repositories
azure-postgres-ts
Connect to Azure Database for PostgreSQL Flexible Server from Node.js/TypeScript using the pg (node-postgres) package. Use for PostgreSQL queries, connection pooling, transactions, and Microsoft Entra ID (passwordless) authentication. Triggers: "PostgreSQL", "postgres", "pg client", "node-postgres", "Azure PostgreSQL…
supabase
Use when doing ANY task involving Supabase. Triggers: Supabase products (Database, Auth, Edge Functions, Realtime, Storage, Vectors, Cron, Queues); client libraries and SSR integrations (supabase-js, @supabase/ssr) in Next.js, React, SvelteKit, Astro, Remix; auth issues (login, logout, sessions, JWT, cookies…
butterbase
AI-native, open-source backend-as-a-service with a built-in Model Context Protocol server. Postgres, auth, storage, functions, AI gateway.
jpa-patterns
JPA/Hibernate patterns and common pitfalls (N+1, lazy loading, transactions, queries). Use when user has JPA performance issues, LazyInitializationException, or asks about entity relationships and fetching strategies.
java-modern
Java 21+ features for Spring Boot - records, sealed classes, pattern matching, virtual threads, text blocks. Use when user asks about modern Java, Java 21 features, or when modernizing existing code.
cohesivity
Use Cohesivity for a project backend only after the user explicitly chooses Cohesivity. Installing or reading this optional skill does not authorize bootstrap, deployment, global installs, or feedback.