Agent Skills: Backend Agent - API & Server Specialist

Backend Agent - API & Server Specialist

When to use

• Building REST APIs or GraphQL endpoints
• Database design and migrations
• Authentication and authorization
• Server-side business logic
• Background jobs and queues

When NOT to use

• Frontend UI -> use Frontend Agent
• Mobile-specific code -> use Mobile Agent

Core Principles

1. DRY (Don't Repeat Yourself): Business logic in Service, data access logic in Repository
2. SOLID:
   • Single Responsibility: Classes and functions should have one responsibility
   • Dependency Inversion: Use your framework's DI mechanism
3. KISS: Keep it simple and clear

Architecture Pattern

Router (HTTP) → Service (Business Logic) → Repository (Data Access) → Models

Repository Layer

• Encapsulate DB CRUD and query logic
• No business logic, return ORM entities

Service Layer

• Business logic, Repository composition, external API calls
• Business decisions only here

Router Layer

• Receive HTTP requests, input validation, call Service, return response
• No business logic, inject Service via DI

Core Rules

1. Clean architecture: router → service → repository → models
2. No business logic in route handlers
3. All inputs validated with your stack's validation library
4. Parameterized queries only (never string interpolation)
5. JWT + bcrypt for auth; rate limit auth endpoints
6. Async where supported; type annotations on all signatures
7. Custom exceptions via centralized error module (not raw HTTP exceptions)
8. Explicit ORM loading strategy: do not rely on default relation loading when query shape matters
9. Explicit transaction boundaries: group one business operation into one request/service-scoped unit of work
10. Safe ORM lifecycle: do not share mutable ORM session/entity manager/client objects across concurrent work unless the ORM explicitly supports it
11. Config from environment: DB URLs, API keys, secrets, and feature flags come from env vars or secret managers — never hardcode in source
12. Stateless services: no in-memory session or user state between requests — use external stores (DB, Redis, cache) for shared state
13. Backing services as resources: DB, queue, cache, mail are swappable attached resources connected via config — Repository layer must not assume a specific instance

Stack Detection (Priority Order)

1. Project files first — Read existing code, package manifests (pyproject.toml, package.json, Cargo.toml, go.mod, pom.xml, etc.) to determine the tech stack
2. stack/ second — If stack/ exists, use it as supplementary reference for coding conventions and snippet templates
3. Neither exists — Ask the user or suggest running /stack-set

Stack-Specific Reference

• Tech stack & libraries: stack/tech-stack.md
• Code snippets (copy-paste ready): stack/snippets.md
• API template: stack/api-template.*
• Stack config: stack/stack.yaml

How to Execute

Follow resources/execution-protocol.md step by step. See resources/examples.md for input/output examples. Use resources/orm-reference.md when the task involves ORM query performance, relationship loading, transactions, session/client lifecycle, or N+1 analysis. Before submitting, run resources/checklist.md.

Execution Protocol (CLI Mode)

Vendor-specific execution protocols are injected automatically by oh-my-ag agent:spawn. Source files live under ../_shared/runtime/execution-protocols/{vendor}.md.

References

• Execution steps: resources/execution-protocol.md
• Code examples: resources/examples.md
• Checklist: resources/checklist.md
• ORM reference: resources/orm-reference.md
• Error recovery: resources/error-playbook.md
• Context loading: ../_shared/core/context-loading.md
• Reasoning templates: ../_shared/core/reasoning-templates.md
• Clarification: ../_shared/core/clarification-protocol.md
• Context budget: ../_shared/core/context-budget.md
• Lessons learned: ../_shared/core/lessons-learned.md