medusa-development

medusa-development is a skill for Claude Code, Codex from finsilabs/awesome-ecommerce-skills. It costs 26 tokens per session (4,399 once invoked), scanned B, original, MIT.

A guide to extending Medusa, an open-source backend for online shops, with custom code. It covers services, event handlers, API routes, data models, workflows, admin changes, and connections to other business systems.

In plain words
What is it for?
It is for building custom commerce backends, adding storefront or admin APIs, reacting to events such as new orders, and connecting systems such as stock, payment, fulfilment, or ERP tools.
Why use it?
It gives developers patterns for adapting a shop backend to business rules that the standard platform does not cover.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Codex; mentions Gemini CLI; mentions OpenCode.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is import { LOYALTY_MODULE } from '../modules/loyalty';.

Good fit It is for building custom commerce backends, adding storefront or admin APIs, reacting to events such as new orders, and connecting systems such as stock, payment, fulfilment, or ERP tools.

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Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/finsilabs/awesome-ecommerce-skills
agentmods
npx agentmods add skills/finsilabs/awesome-ecommerce-skills/medusa-development

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for medusa-development

README.md
[![agentmods](https://agentmods.dev/badge/skills/finsilabs/awesome-ecommerce-skills/medusa-development/github.svg)](https://agentmods.dev/skills/finsilabs/awesome-ecommerce-skills/medusa-development)
Your own site
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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.

agentmods 80×15 button for medusa-development

Your own site · 80×15
<a href="https://agentmods.dev/skills/finsilabs/awesome-ecommerce-skills/medusa-development"><img src="https://agentmods.dev/badge/skills/finsilabs/awesome-ecommerce-skills/medusa-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,399 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00026 $0.04399
Opus 5 $0.00013 $0.02200
Sonnet 5 $0.00005 $0.00880
Haiku 4.5 $0.00003 $0.00440

Measured 12d ago against content hash 071f55cae10e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade B, and why

medusa-development scanned grade B with 1 finding 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 12d 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.

Sends data to an external URLmediumData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

const response = await fetch('https://api.custompay.com/v1/sessions', { method: 'POST',
skills/headless-modern/medusa-development/SKILL.md · 548 lines

How it starts

The opening of the file, as written. The whole thing — 548 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Medusa.js Development

Overview

Build and extend headless e-commerce backends with Medusa.js using custom services, subscribers (event handlers), API route extensions, custom entities with migrations, and module architecture. This skill covers Medusa v2 project setup, the dependency injection container, custom workflows, admin UI extensions, and integration patterns for connecting Medusa to storefronts, ERPs, and payment providers.

When to Use This Skill

  • When setting up a new headless e-commerce backend with Medusa
  • When building custom business logic as Medusa services and workflows
  • When extending the Medusa API with custom endpoints for storefront or admin use
  • When implementing event-driven automation via subscribers (e.g., send email on order placed)
  • When integrating external systems (ERP, CMS, fulfillment) with Medusa

Prerequisites & Platform Notes

This skill is written for custom/headless storefronts (Node.js, Python, or similar backend). The code examples use TypeScript/Node.js and can be adapted to any stack.

Shopify: Shopify Hydrogen is Shopify's headless framework. MACH/composable patterns apply when using Shopify as the commerce backend with a custom frontend, or when mixing Shopify with other best-of-breed services. WooCommerce: WooCommerce can serve as a headless backend via its REST API and WPGraphQL. These patterns apply when decoupling the frontend from WordPress. Magento: Magento's GraphQL API and PWA Studio support headless architectures. These composable patterns apply to Magento as a backend service in a MACH stack.

You'll need:

  • Node.js 18+ (or adapt to your backend language)
  • PostgreSQL (or your preferred relational database)
  • Redis for caching/queues
  • Stripe account and API keys
  • An email sending service (SendGrid, AWS SES, or Postmark)

Core Instructions

  1. Set up a Medusa project

    # Create a new Medusa project
    npx create-medusa-app@latest my-store
    
    # Project structure (Medusa v2)
    # my-store/
    # ├── src/
    # │   ├── api/           # Custom API routes
    # │   ├── jobs/          # Scheduled jobs
    # │   ├── links/         # Module links
    # │   ├── modules/       # Custom modules
    # │   ├── subscribers/   # Event subscribers
    # │   └── workflows/     # Custom workflows
    # ├── medusa-config.ts
    # └── package.json
    
    # Start the development server
    npx medusa develop
    

Read the full file on GitHub · 548 lines

Changes

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.

  1. 12d ago First seen · 548 lines · 26 tokens per session scan B 071f55cae10e

Subscribe to this mod's changes

medusa-development is a skill published in the GitHub repository finsilabs/awesome-ecommerce-skills (52 stars, last pushed 6mo ago), licensed MIT. It adds 26 tokens to every session and 4,399 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 1 finding (sends data to an external url). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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