api-design

A guide for designing public APIs that remain compatible as they change. An API is the agreed interface that other programs use to communicate with a library or service.

In plain words
What is it for?
Use it when planning APIs, checking wire compatibility, managing versioning, or evolving NuGet packages and distributed services.
Why use it?
It helps prevent new changes from breaking existing users, integrations, or distributed systems. It focuses on adding capabilities without removing or unexpectedly changing old ones.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/f-u-s-e-e/fusedevelopmentgroup/csharp-api-design
Any agent
npx skills add F-U-S-E-E/FuseDevelopmentGroup --skill csharp-api-design
Clone the repo
git clone --depth 1 https://github.com/F-U-S-E-E/FuseDevelopmentGroup

Made for: Claude Code, Codex.

Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,426 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00033 $0.02426
Opus 5 $0.00016 $0.01213
Sonnet 5 $0.00007 $0.00485
Haiku 4.5 $0.00003 $0.00243

Measured 2d ago against content hash 8cb6581a701d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-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 2d 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.

.claude/skills/csharp-api-design/SKILL.md · 388 lines

The source is not reproduced here

Licensed AGPL-3.0

The repository is licensed AGPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

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. 2d ago First seen · 388 lines · 33 tokens per session scan A 8cb6581a701d

Subscribe to this mod's changes

api-design is a skill published in the GitHub repository F-U-S-E-E/FuseDevelopmentGroup (21 stars, last pushed 8d ago), licensed AGPL-3.0. It adds 33 tokens to every session and 2,426 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 2026-08-30.

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