API and Interface Design
Design stable, well-documented interfaces that are hard to misuse — Hyrum's Law, contract-first, the one-version rule
- What
- Design stable, well-documented interfaces that are hard to misuse — Hyrum's Law, contract-first, the one-version rule
- Cost
- Free
- Needs
- none — a public interface to design or review
- Install
- Copy the installer prompt below into your Muse — your agent does the rest.
Curated by Skill Harbor — an interface-design skill from Addy Osmani's engineering workflow collection: make the right thing easy and the wrong thing hard. It walks through Hyrum's Law (every observable behavior becomes a de facto contract), the one-version rule (extend rather than fork), contract-first design (define the interface before implementing it), and planning for deprecation at design time. Applies to REST APIs, GraphQL schemas, module boundaries, component props — any surface where one piece of code talks to another. Distinct from the already-published addyosmani skills — none of them cover API surface design. By @addyosmani, listed here with credit to its creator. Honest caveats: design guidance only — it won't generate your OpenAPI spec; following it means saying no to "just expose this one internal field," which is the whole point and also the hard part. Skill Harbor never reviews the code, review it yourself before use.
Version:
Install
Prerequisites: none — a public interface to design or review Install "API and Interface Design" for me. Design stable, well-documented interfaces that are hard to misuse — Hyrum's Law, contract-first, the one-version rule Repository: https://github.com/addyosmani/agent-skills/blob/main/skills/api-and-interface-design/SKILL.md 1. Fetch the SKILL.md file for the addyosmani-api-and-interface-design skill from the repository into a temporary folder and summarize what it does in one or two sentences. 2. Safety check: review the SKILL.md and scripts for anything suspicious (unexpected network calls, shell commands, credential harvesting). This repo should contain zero secrets in code, credentials only via the secure vault, allowed hosts declared in the SKILL.md. Verify that holds here; STOP on any red flag and tell me. 3. Install it as a skill: copy SKILL.md and its helper files into the agent's skills directory, in a folder named "addyosmani-api-and-interface-design". 4. Verify with no network calls: frontmatter valid, files in place. 5. Report what was installed, where, and what I still need to do myself (e.g. any accounts, API keys, or CLI tools mentioned in the prerequisites above). GitHub is optional: if I have a GitHub account or the gh CLI, you may use it; otherwise public access is fine. Never require it unless it's in the prerequisites above. Rules: don't touch anything outside the temp folder and the install target. Never ask me to paste secrets in chat — credentials go through the secure vault or environment variables. If anything looks off, stop and ask me.
Questions
How do I install a build?
Every product page includes a copy-paste install prompt. Paste it into your Muse and it sets the build up for you — no manual configuration.
Where does my money go?
Straight to the seller. Skill Harbor never processes payments: checkout happens on the seller’s own page, usually Stripe.
What does the ✓ next to a creator’s name mean?
It means we confirmed the identity of the person behind the listing. It says nothing about the code itself — always check a build before installing it.