Backend

Spring Boot 프로젝트의 유닛테스트를 작성합니다.JUnit, Mockito를 사용하며 Fixtures 패턴으로 테스트 객체를 관리합니다.사용 시점: 서비스 로직, 컨트롤러, 리포지토리 테스트 작성

Essential patterns for polkadot-api (PAPI) development. Use when implementing blockchain interactions with Polkadot/Substrate chains including transactions (signing, batching, watching), queries (storage, multi-key), observables (lifecycle tracking), type handling (MultiAddress, Binary), client setup, or debugging PAPI code. Critical for preventing the common mistake of using @polkadot/api (PJS) instead of polkadot-api (PAPI). Load whenever user mentions polkadot-api, blockchain transactions, pallet calls, or needs to fix PAPI-related type errors.

Browser automation using the browser MCP for web scraping, form filling, content extraction, and macro execution. Use when user asks to open websites, search pages, extract data, fill forms, or automate browser tasks.

Use when creating or editing Mermaid flowchart diagrams, encountering parse errors, or unsure about node shapes, connection syntax, or styling - provides syntax guardrails using modern shape syntax for Obsidian-compatible diagrams

Initialize long-running agent projects with environment setup, feature list generation, and progress tracking. Use when starting a new implementation project or setting up an existing codebase for Claude-assisted development. Creates init.sh (dev server script), claude-progress.txt (work log), and docs/features.json (feature list with status tracking).

Spring Boot with Kotlin - controllers, services, coroutines

Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).

Spring Boot 4 testing strategies and patterns. Use when writing unit tests, slice tests (@WebMvcTest, @DataJpaTest), integration tests, Testcontainers with @ServiceConnection, security testing (@WithMockUser, JWT), or Modulith event testing with Scenario API. Covers the critical @MockitoBean migration from @MockBean.

Create validation logic for F# backends with error accumulation and async validation.Use when: "add validation", "validate X", "input validation", "complex validation","business rules", "check email", "required fields", "async validation","database uniqueness", "cross-field validation", "validation errors".Creates validators in src/Server/Validation.fs. Use for complex scenarios;basic validation patterns are in fsharp-backend skill.

Provides documentation standards for README, API docs, code comments, changelogs, and project cleanup. Use when writing documentation, README files, API references, or cleaning up project files.

Systematic debugging for Encore.ts backend incidents using diagnostic scripts, database queries, and structured logging. Use when backend tests fail, services crash, or async flows stall.

Perigon ASP.NET Core + EF Core + Aspire conventions

Comprehensive guide to building production-ready REST APIs in Rails with serialization, authentication, versioning, rate limiting, and testing

Generates Django models with proper field types, relationships, and migrations. Use when creating Django models or database schemas.

Implement F# backend using Giraffe + Fable.Remoting with proper layer separation.Use when: "implement backend", "add API", "create endpoint", "server logic", "business rules","backend for X", "API implementation", "server-side", "Giraffe", "Fable.Remoting".Layers: Validation → Domain (pure) → Persistence (I/O) → API.Creates code in src/Server/: Validation.fs, Domain.fs, Persistence.fs, Api.fs.

Model Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.

Handle loading states in the portal app using Flask loaders. Use when adding loading indicators to buttons, cards, pages, or any async operations.

Best practices for Laravel API Resources including resource transformation, collection handling, conditional attributes, and relationship loading.

Maps complete data flows from UI components through API services, backend endpoints, Genkit flows, to database operations. Generates visual architecture diagrams.

Apply when validating external data (API inputs, form data, environment variables) with TypeScript type inference.