api-and-interface-design

api-and-interface-design is a skill for Claude Code from FluxonLab/Skillry. It costs 31 tokens per session (2,335 once invoked), scanned A, original, no licence file.

A design guide for APIs and the agreements between software modules, servers, and user interfaces. REST and GraphQL are common ways for applications to exchange data.

In plain words
What is it for?
Use it to design REST or GraphQL endpoints, public interfaces, type contracts, module boundaries, and frontend-backend agreements.
Why use it?
It helps prevent breaking changes and mismatched expectations between the parts of an application.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the skillry-backend-and-api plugin — 6 skills, 6 agents shipped together

Good fit Use it to design REST or GraphQL endpoints, public interfaces, type contracts, module boundaries, and frontend-backend agreements.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/fluxonlab/skillry/12-api-and-interface-design
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add FluxonLab/Skillry --skill 12-api-and-interface-design
Clone the repo
git clone --depth 1 https://github.com/FluxonLab/Skillry

Made for: Claude Code.

Or install skillry-backend-and-api, the plugin that ships this one along with the rest of its 6 skills, 6 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for api-and-interface-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/fluxonlab/skillry/12-api-and-interface-design.svg)](https://agentmods.dev/skills/fluxonlab/skillry/12-api-and-interface-design)
Your own site
<a href="https://agentmods.dev/skills/fluxonlab/skillry/12-api-and-interface-design"><img src="https://agentmods.dev/badge/skills/fluxonlab/skillry/12-api-and-interface-design.svg" alt="Measured on agentmods" height="20"></a>
Per session 31 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,335 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00031 $0.02335
Opus 5 $0.00015 $0.01167
Sonnet 5 $0.00006 $0.00467
Haiku 4.5 $0.00003 $0.00233

Measured 4d ago against content hash 8a074df97e9c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

api-and-interface-design scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/backend-and-api/skills/12-api-and-interface-design/SKILL.md · 311 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 311 lines · 31 tokens per session scan A 8a074df97e9c

Subscribe to this mod's changes

api-and-interface-design is a skill published in the GitHub repository FluxonLab/Skillry (2 stars, last pushed 9d ago), with no licence file. It adds 31 tokens to every session and 2,335 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.