Guide · Agent skill
How to use the Replica Backend Builder agent skill (replica-backend)
Updated · written with AI from the project's own documentation and checked against our catalogue data
The replica-backend skill is an add-on for an AI coding agent that builds the server side of an app clone: sign-in, a database with access rules, Stripe subscription payments in test mode, transactional email, scheduled jobs and official-API integrations. It is aimed at developers prototyping an app, students learning how auth, row-level security and Stripe webhooks fit together, and teams building a fake-data demo. This guide explains what the skill does, how to install it, how to trigger it, and what you need before you start.
Replica Backend BuilderJakeschincariol/replica-skill · MIT Download the skill Quick start
- 1Download the ZIP. Download the replica-backend ZIP from this page and unzip it to get the SKILL.md file.
- 2Choose an install location. Place the folder in ~/.claude/skills/ for all projects, or in .claude/skills/ inside one project. Alternatively, upload it under Settings → Capabilities → Skills in the Claude apps.
- 3Prepare your planning file. Make sure your project contains replica/architecture.md from an earlier planning step, since the skill reads it.
- 4Create your accounts and keys. Create the Stripe, Supabase, Resend or Postmark, and Google Cloud projects yourself, then put the keys in a .env.local file.
- 5Make a natural request. Ask for a specific feature such as adding login, connecting Stripe or sending emails.
- 6Review the output. Check the migrations, server code, .env.example and replica/backend.md before deploying.
- 7Test before going live. Use Stripe test mode and a second test user to verify access rules, then move to the next step, /replica-test.
What is an agent skill, and what does replica-backend do?
An agent skill is a folder containing a SKILL.md file that tells an AI agent when to use a capability and how to carry it out. The agent reads the file when your request matches the skill's description.
replica-backend reads a planned architecture file at replica/architecture.md and writes migrations and server code for it. It also keeps a replica/backend.md progress file up to date with a security checklist.
- User login: email sign up with verification, password reset, and OAuth with your own developer apps
- Sessions using http-only secure cookies, with sign out everywhere
- A database with migrations and access rules, plus a seed script of fake data
- Stripe Checkout for sign up and the Customer Portal for changes, with webhook handling
- Transactional email through Resend or Postmark, and scheduled jobs with retries
- Integrations such as Google Calendar, through official APIs only
Install the replica-backend skill
Download the ZIP from this page and unzip it. The skill is a single file, SKILL.md. Place the folder in one of two locations, depending on how you want to use it.
For all your projects, put it in ~/.claude/skills/. For one project only, put it in the project's .claude/skills/ folder. You can also upload the skill in the Claude apps under Settings → Capabilities → Skills.
- Personal install: ~/.claude/skills/ (available across projects)
- Project install: .claude/skills/ inside your project folder (available only there)
- Claude apps: Settings → Capabilities → Skills, then upload
Trigger the skill with natural requests
You do not need to name the skill. The agent uses it when your request matches the description in SKILL.md. Phrases the description lists include "add login", "set up auth", "wire up the database", "add payments", "connect Stripe", "add Google Calendar", "send emails" and "backend for my clone". The skill also runs when /replica-build is running on fake data.
Be specific about the feature. "Add login" is clear; "make it better" is not.
Example requests
These are requests that match the skill's trigger phrases. Each one should be made inside a project that already has replica/architecture.md.
- "Set up auth for my clone with email sign up and password reset."
- "Wire up the database and add access rules so a second user gets nothing back."
- "Connect Stripe in test mode and add a monthly plan with Checkout."
- "Add Google Calendar sync to the backend."
- "Send a welcome email through Resend from my own domain."
What you need before you start
The skill reads a planning file produced by an earlier step, and it expects you to create the accounts and keys yourself. Claude does not sign up for services, type passwords, or enter card details or live keys.
- Node.js or a compatible runtime for the server code and npm audit
- Accounts and API keys you create: Stripe, Supabase, Resend or Postmark, and Google Cloud if you use calendar integration
- A .env.local file that you fill in with your keys. The skill writes .env.example with variable names only, no values
- A replica/architecture.md file from an earlier planning step
Safety notes: scripts and network access
This skill runs scripts and uses the network. Review the migrations, generated code and environment settings before you deploy anything. The skill's own rules require official public APIs with your own keys, test mode first, and no calls to the original app's private endpoints.
Keep secrets in environment variables and out of client code. The checklist asks for .env* files to be listed in .gitignore and for dependencies to be audited with npm audit.
- Use Stripe test keys and test cards until you deliberately move to live mode
- Confirm that a second test user cannot read another user's records
- Check that webhooks verify signatures before you rely on them
- Google scopes such as Calendar need Google's OAuth verification before public launch, which can take weeks
Tips for better results
Give the skill a complete plan first. Its output depends on replica/architecture.md, and features missing from the plan will not be built.
Ask for one area at a time, then check backend.md before moving on. The checklist shows what is ticked and what is still open.
- Keep the .env.local file out of version control
- Start Google verification early if you plan calendar integration, and note it in backend.md
- Expect the skill to hand off testing to the next step, /replica-test
What people use it for
- Prototyping a web or mobile app with working login and a database in one session
- Learning how row-level security, sessions and Stripe webhooks work together by reading generated code
- Building a fake-data demo with seed scripts that you later connect to real accounts
- Adding Stripe Checkout and the Customer Portal to an existing clone, in test mode
- Setting up scheduled reminders or digests with retries and a dead-letter log
Frequently asked questions
Is the replica-backend skill free?
The skill is licensed under MIT, as stated on this page. The third-party services it connects to, such as Stripe, Supabase, Resend or Postmark and Google Cloud, have their own accounts and terms, which you create and manage yourself.
What do I need to install and use replica-backend?
You need Node.js or a compatible runtime, accounts and API keys for the services you use, a .env.local file you fill in, and a replica/architecture.md file from an earlier planning step. Install the ZIP into ~/.claude/skills/ or a project's .claude/skills/ folder, or upload it under Settings → Capabilities → Skills.
How do I trigger the replica-backend skill?
Make a natural request that matches its description, such as "add login", "set up auth", "connect Stripe" or "send emails". You do not need to type the skill name.
Does the skill handle real customer payments?
The skill is built to use Stripe test mode first and test cards until deployment. Its own description says it does not replace a security audit, so review the code and settings before handling real payments or personal data.
Can I use it to copy a competitor's app?
No. The skill uses only official public APIs with your own keys and never calls the original app's private endpoints or reuses its credentials. It is not meant for copying private APIs or branding, which can breach terms of service.
What should I use instead if I cannot review generated code?
If you cannot review generated code, migrations and environment settings, the skill is not a good fit, because the skill's guidance assumes a developer checks the output before deploying. Consider working with a developer or a managed backend platform instead.
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Our verdict
Use replica-backend if you are a developer or student who wants a working backend scaffold for a prototype or fake-data demo, and you are comfortable reviewing the code it writes. Pick something else if you need to launch a product that handles real payments or personal data without a security review, or if you want to clone an app using its private APIs or branding.
Download the skill