api-and-interface-design SKILL.md skillA

This file is byte-identical to the first copy the registry indexed. Same content hash, so the same checks give both the same grade.

api-and-interface-design from francostino/opencode-skills-collection is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

mdr add francostino/opencode-skills-collection/api-and-interface-design@git:20260730.90257ed

Pins git:20260730.90257ed in mdr.lock. Pin the fingerprint instead.

Audit grade

A, 17 of 17 checks passed

Kind

SKILL.md skill

Repository

francostino/opencode-skills-collection

Path

bundled-skills/api-and-interface-design/SKILL.md

Versions recorded

2

Latest version

git:20260730.90257ed, committed Jul 30, 2026

First version recorded

Jul 7, 2026

Size

10,958 bytes

Repository stars

87

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 francostino/opencode-skills-collection/api-and-interface-design@sha256:9e0ed660e3b9249e

[![mdr](https://markdownregistry.com/badge/art_vxugro3kcmvbpbv7.svg)](https://markdownregistry.com/a/art_vxugro3kcmvbpbv7)

Versions

The registry has recorded 2 versions of this file, between Jul 7, 2026 and Jul 30, 2026, about one every 23 days.

Audit of the latest version

Source

API

GET https://markdownregistry.com/api/v1/artifacts/art_vxugro3kcmvbpbv7
GET https://markdownregistry.com/api/v1/resolve?ref=francostino/opencode-skills-collection/api-and-interface-design
GET https://markdownregistry.com/api/v1/blob/9e0ed660e3b9249e77cd55bb43cfc7279e3ec0567db6c66b89c581763264963e

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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