A set of backend engineering guidelines for Python FastAPI and Node.js services, including API structure, validation, authentication, and error handling.

It guides developers in organizing backend layers, designing REST or gRPC APIs, validating requests, handling errors, and applying access controls.

It helps prevent inconsistent API designs, weak input checks, unclear errors, and mixed-up business and transport code.

How LionelHuanSi/awesome-ai-agent-skills configures Claude Code and Co

Reuse

Borrowing it

Nothing to install: this file belongs to LionelHuanSi/awesome-ai-agent-skills. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/LionelHuanSi/awesome-ai-agent-skills/main/.agents/skills/backend-api/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/LionelHuanSi/awesome-ai-agent-skills

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/lionelhuansi/awesome-ai-agent-skills/backend-api/github.svg)](https://agentmods.dev/skills/lionelhuansi/awesome-ai-agent-skills/backend-api)

Your own site

<a href="https://agentmods.dev/skills/lionelhuansi/awesome-ai-agent-skills/backend-api"><img src="https://agentmods.dev/badge/skills/lionelhuansi/awesome-ai-agent-skills/backend-api/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/lionelhuansi/awesome-ai-agent-skills/backend-api"><img src="https://agentmods.dev/badge/skills/lionelhuansi/awesome-ai-agent-skills/backend-api.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 350 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. 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.

Model	Per session	Once invoked
Fable 5.1	$0.00041	$0.00350
Opus 5	$0.00020	$0.00175
Sonnet 5	$0.00008	$0.00070
Haiku 4.5	$0.00004	$0.00035

Measured 11d ago against content hash 50ace815a674, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

backend-api 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 11d 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.

.agents/skills/backend-api/SKILL.md · 32 lines

What it actually says

Backend Engineering & API Design Skill

Sourced from PatrickJS/awesome-cursorrules for robust FastAPI, Node.js, and API architecture.

Architecture & Layering Rules

Clean Architecture / Domain-Driven Design (DDD):
- Controllers/Routers: Transport layer (HTTP/gRPC) handling request parsing and response formatting.
- Service/Domain Layer: Core business logic, completely decoupled from HTTP frameworks.
- Data Access Layer: Repositories/DAOs encapsulating database interactions.

API Design Standards

1. Request Validation & Schema Integrity

Python: Use Pydantic V2 models for strict type validation, field constraints (Field(gt=0)), and custom validators.
TypeScript: Use Zod or TypeBox schemas to validate runtime API payloads.

2. Error Handling & Standard Responses

Use structured JSON error responses with standard error codes and human-readable messages.
Catch domain exceptions at service boundaries and map cleanly to HTTP status codes.

3. Security Standards

Authentication: JWT validation with expiration verification and key rotation.
Authorization: Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC) enforced at router middleware.
CORS & Headers: Strict CORS origin whitelisting, Security headers.

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.

11d ago First seen · 32 lines · 41 tokens per session scan A 50ace815a674

Subscribe to this mod's changes

backend-api is a skill published in the GitHub repository LionelHuanSi/awesome-ai-agent-skills (3 stars, last pushed 1mo ago), licensed MIT. It adds 41 tokens to every session and 350 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 2026-08-31.

Backend and APIs

mem0-oss-to-platform

Plan and then execute a migration of a project from the mem0 open-source / self-hosted SDK (the local Memory class) to the mem0 Platform / hosted / managed SDK (the MemoryClient class). Use this whenever a developer wants to move, switch, or migrate their mem0 usage off OSS/self-hosted to the hosted API — e.g.…

mem0ai/mem0 · 273 tokens

agui-dotnet-protobuf

Use the protobuf wire transport (instead of the default Server-Sent Events) for an AG-UI connection with the AG-UI .NET SDK — a compact binary event stream negotiated via the Accept header. USE FOR: making an AGUIChatClient prefer protobuf by wiring an AGUIEventStreamHandler with ProtobufEventStreamFormatter (then…

ag-ui-protocol/ag-ui · 162 tokens

azure-mgmt-botservice-dotnet

Azure Resource Manager SDK for Bot Service in .NET. Management plane operations for creating and managing Azure Bot resources, channels (Teams, DirectLine, Slack), and connection settings. Triggers: "Bot Service", "BotResource", "Azure Bot", "DirectLine channel", "Teams channel", "bot management .NET", "create bot".

microsoft/skills · 78 tokens

fastapi-router-py

Create FastAPI routers with CRUD operations, authentication dependencies, and proper response models. Use when building REST API endpoints, creating new routes, implementing CRUD operations, or adding authenticated endpoints in FastAPI applications.

microsoft/skills · 46 tokens

aws-sdk-java-v2-core

Provides AWS SDK for Java 2.x client configuration, credential resolution, HTTP client tuning, timeout, retry, and testing patterns. Use when creating or hardening AWS service clients, wiring Spring Boot beans, debugging auth or region issues, or choosing sync vs async SDK usage.

giuseppe-trisciuoglio/developer-kit · 62 tokens

migrate-segw-to-rap

Reverse-engineer a SEGW-built OData V2 service (MPC/DPC/MPCEXT/DPCEXT) into a modern RAP V4 service — tables, CDS views (interface + projection), behavior definitions, draft entities, service definition + binding. Use when asked to "migrate this SEGW service to RAP", "convert OData V2 to V4 RAP", "modernize this…

arc-mcp/arc-1 · 106 tokens

awesome-ai-agent-skills: Skill for Claude Code