Use when building C# applications with .NET 8+, ASP.NET Core APIs, or Blazor web apps. Builds REST APIs using minimal or controller-based routing, configures database access with Entity Framework Core, implements async patterns and cancellation, structures applications with CQRS via MediatR, and scaffolds Blazor components with state management. Invoke for C#, .NET, ASP.NET Core, Blazor, Entity Framework, EF Core, Minimal API, MAUI, SignalR.
api-designer
api-designer is an open-source backend skill for Claude Code and compatible agents, published by Jeffallan. Its author describes it as: “Use when designing REST or GraphQL APIs, creating OpenAPI specifications, or planning API architecture. Invoke for resource modeling, versioning strategies, pagination patterns, error handling standards.”. The project has 11k stars on GitHub and is available under the MIT license. Add it to your setup with `/plugin marketplace add Jeffallan/claude-skills`.
What api-designer does
Senior API architect specializing in REST and GraphQL APIs with comprehensive OpenAPI 3.1 specifications.
Installation
Add api-designer to your agent with:
/plugin marketplace add Jeffallan/claude-skillsAlways review a skill's source before installing it. This command comes from the skill's public repository; the linked repo is the source of truth for exact setup steps.
What's inside
The SKILL.md for api-designer is organised into these sections:
- Core Workflow
- Reference Guide
- Constraints
- MUST DO
- MUST NOT DO
- Templates
- OpenAPI 3.1 Resource Endpoint (copy-paste starter)
- RFC 7807 Error Response (copy-paste)
- Output Checklist
- Knowledge Reference
When to use it
Reach for api-designer when you want backend help from your agent without writing the same instructions every session. Load the skill and the agent picks it up automatically for relevant tasks.
Strengths
- Clear MIT license — safe to read and adapt
- Ships in Jeffallan/claude-skills, an established project with 11,060 GitHub stars
- Actively maintained (recent commits)
Topics
Frequently asked questions
- What does api-designer do?
- Use when designing REST or GraphQL APIs, creating OpenAPI specifications, or planning API architecture. Invoke for resource modeling, versioning strategies, pagination patterns, error handling standards.
- How do I install api-designer?
- Run /plugin marketplace add Jeffallan/claude-skills in your agent, then reload your skills. Review the source at https://github.com/Jeffallan/claude-skills before installing.
- Is api-designer free to use?
- Yes. api-designer is free and open source under the MIT license, so you can read, run, and adapt it within that license's terms.
- Where does api-designer come from?
- api-designer ships inside Jeffallan/claude-skills, a repository that contains 41 catalogued skills in total. The repository's 11,060 GitHub stars apply to that whole collection, not to this skill on its own.
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