Overview
api-and-interface-design is an open-source backend skill for Claude Code and compatible agents, published by addyosmani. Its author describes it as: “Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing bounda…”. The project has 98k stars on GitHub and is available under the MIT license. Add it to your setup with `/plugin marketplace add addyosmani/agent-skills`.
What api-and-interface-design does
Design stable, well-documented interfaces that are hard to misuse. Good interfaces make the right thing easy and the wrong thing hard. This applies to REST APIs, GraphQL schemas, module boundaries, component props, and any surface where one piece of code talks to another.
What’s inside
The SKILL.md for api-and-interface-design is organised into these sections:
- Overview
- When to Use
- Core Principles
- Hyrum's Law
- The One-Version Rule
- 1. Contract First
- 2. Consistent Error Semantics
- 3. Validate at Boundaries
- 4. Prefer Addition Over Modification
- 5. Predictable Naming
- 6. Honouring an Idempotency Key
- REST API Patterns
Installation
Add api-and-interface-design to your agent with:
/plugin marketplace add addyosmani/agent-skillsReview a skill’s source before installing it — skills can instruct your agent to run commands. This command comes from the skill’s public repository, which is the source of truth for setup steps. New to skills? Read how to install Claude Code skills.
Supported agents
- Claude Code — ships a claude code plugin marketplace
- Codex — declared in the repository topics
- Cursor — declared in the repository topics
- Antigravity — declared in the repository topics
License
api-and-interface-design is published under the MIT license.
Strengths
- Clear MIT license — safe to read and adapt within its terms
- Ships in addyosmani/agent-skills, an established project with 97,992 GitHub stars
- Works with Claude Code, Codex, Cursor, Antigravity
- Actively maintained — repository updated in the last 30 days
- Its repository gained 16,916 GitHub stars over the last 52 days
Author
Topics
Alternatives to api-and-interface-design
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Frequently asked questions
- What does api-and-interface-design do?
- Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.
- How do I install api-and-interface-design?
- Run /plugin marketplace add addyosmani/agent-skills in your agent, then reload your skills. Review the source at https://github.com/addyosmani/agent-skills before installing.
- Is api-and-interface-design free to use?
- Yes. api-and-interface-design is free and open source under the MIT license, so you can read, run, and adapt it within that license's terms.
- Which agents does api-and-interface-design work with?
- api-and-interface-design lists Claude Code, Codex, Cursor, and Antigravity — named in its SKILL.md, its plugin marketplace or its repository topics. Skills use the portable SKILL.md format, so other agents that read that format may load it too.
- Where does api-and-interface-design come from?
- api-and-interface-design ships inside addyosmani/agent-skills, a repository that contains 26 catalogued skills in total. The repository's 97,992 GitHub stars apply to that whole collection, not to this skill on its own.
