api-and-interface-design SKILL.md skillA
api-and-interface-design from addyosmani/agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add addyosmani/agent-skills/api-and-interface-design@git:20261019.63128d0Pins git:20261019.63128d0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- addyosmani/agent-skills
- Path
skills/api-and-interface-design/SKILL.md- Versions recorded
- 7
- Latest version
- git:20261019.63128d0, committed Oct 19, 2026
- First version recorded
- Mar 28, 2026
- Size
- 14,938 bytes
- Repository stars
- 112,362
- License
- MIT
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.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# API and Interface Design ## Overview 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. ## When to Use - Designing new API endpoints - Defining module boundaries or contracts between teams - Creating component prop interfaces - Establishing database schema that informs API shape - Changing existing public interfaces ## Core Principles ### Hyrum's Law > With a sufficient number of users of an API, all observable behaviors of your system will be depended on by somebody, regardless of what you promise in the contract. This means: every public behavior — including undocumented quirks, error message text, timing, and ordering — becomes a de facto contract once users depend on it. Design implications: - **Be intentional about what you expose.** Every observable behavior is a potential commitment. - **Don't leak implementation details.** If users can observe it, they will depend on it. …
Read the whole file at its exact version.
How to install
mdr add addyosmani/agent-skills/api-and-interface-design@sha256:cc5e2166c484b2c2The line at the top of this page pins the label git:20261019.63128d0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_bqep7hipv2rjthjn)
4 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 7 versions of this file, between Mar 28, 2026 and Oct 19, 2026, about one every 34 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261019.63128d0 latest | 2026-10-19 | 63128d0 | 14,938 B | A | view · diff |
| git:20261002.5f78656 | 2026-10-02 | 5f78656 | 14,886 B | A | view · diff |
| git:20260813.ce89b03 | 2026-08-13 | ce89b03 | 14,884 B | A | view · diff |
| git:20260331.fea75b1 | 2026-03-31 | fea75b1 | 10,307 B | A | view · diff |
| git:20260331.702a894 | 2026-03-31 | 702a894 | 10,267 B | A | view · diff |
| git:20260328.8739c15 | 2026-03-28 | 8739c15 | 10,272 B | A | view · diff |
| git:20260328.4d0b832 | 2026-03-28 | 4d0b832 | 8,822 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (14938 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
addyosmani/agent-skills · 112,362 stars · license MIT · pushed 2026-10-31 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_bqep7hipv2rjthjn GET https://markdownregistry.com/api/v1/resolve?ref=addyosmani/agent-skills/api-and-interface-design GET https://markdownregistry.com/api/v1/blob/cc5e2166c484b2c297e8253f56e7525e5031f81d66101ca4e760ef378ea6bad0
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.
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