Is the API And Interface Design skill free?

Yes. The skill itself is free from addyosmani/agent-skills. SkillProof publishes the install command and an independent test verdict at no cost.

What is the API And Interface Design SkillProof Score?

9.6/10 — installs cleanly 5/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 5/5.

How do I install API And Interface Design?

Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.

Can I use API And Interface Design with Cursor, Copilot, Gemini CLI, Codex or other AI tools?

The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.

API And Interface Design

Checklist-driven REST/GraphQL and TypeScript interface design with error and naming rules

by addyosmani · addyosmani/agent-skills

Tested · Works

Install — copy the command Download source ↗

Test report

Verdict: Tested · Works
Score: 9.6/10
Tested: Jul 10, 2026
Environment: Claude Code 2.x (agent harness)
Upstream re-checked: Aug 10, 2026 · 012c8b6

Turned a verb-based API design (POST /createBookmark, inconsistent returns) into proper resource routes, one consistent error shape, cursor pagination and a branded ID type.

Scored on four weighted criteria — install, triggering, output vs. baseline, docs. How scoring works

Installs cleanly 5/5
Triggers reliably 5/5
Output vs. baseline 9/10
Docs & honesty 5/5

What API And Interface Design does

Guides designing stable REST/GraphQL endpoints, module boundaries, and TypeScript type contracts using Hyrum's Law, consistent error semantics, boundary validation, and additive-only changes. Triggers when a user is designing new endpoints, defining contracts between frontend/backend or modules, or changing an existing public interface.

How to install API And Interface Design

git clone https://github.com/addyosmani/agent-skills
cd agent-skills
mkdir -p ~/.claude/skills
cp -r skills/api-and-interface-design ~/.claude/skills/api-and-interface-design

Skills live in ~/.claude/skills/ (global) or .claude/skills/ (per-project). Restart Claude Code after installing.

Commands — how to trigger API And Interface Design

/api-and-interface-design Checklist-driven REST/GraphQL and TypeScript interface design with error and naming rules

It also activates on plain-language prompts like these:

Design a REST endpoint for order refunds with consistent error semantics
Define the TypeScript contract between the frontend and this new service
Review this public API change for additive-only compatibility

Frequently asked questions

Is the API And Interface Design skill free?: Yes. The skill itself is free from addyosmani/agent-skills. SkillProof publishes the install command and an independent test verdict at no cost.
Does API And Interface Design work with Claude Code?: We tested it with Claude Code 2.x (agent harness) on Jul 10, 2026. Verdict: Tested · Works. Turned a verb-based API design (POST /createBookmark, inconsistent returns) into proper resource routes, one consistent error shape, cursor pagination and a branded ID type.
What is the API And Interface Design SkillProof Score?: 9.6/10 — installs cleanly 5/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 5/5.
How do I install API And Interface Design?: Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.
Can I use API And Interface Design with Cursor, Copilot, Gemini CLI, Codex or other AI tools?: The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.