api-design

A guide for designing interfaces between pieces of software, such as functions, modules, endpoints, or libraries. It treats an API as a contract describing inputs, outputs, errors, and side effects.

In plain words
What is it for?
Choosing function and endpoint shapes, defining types and errors, setting safe defaults, matching surrounding conventions, and evolving interfaces without unnecessary breaking changes.
Why use it?
It reduces accidental misuse and future maintenance by keeping the public surface small, predictable, consistent, and easier to change safely.

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/new1direction/korgex/api-design
Any agent
npx skills add New1Direction/korgex --skill api-design
Clone the repo
git clone --depth 1 https://github.com/New1Direction/korgex

Made for: Claude Code, Codex.

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 345 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00017 $0.00345
Opus 5 $0.00009 $0.00172
Sonnet 5 $0.00003 $0.00069
Haiku 4.5 $0.00002 $0.00034

Measured 2d ago against content hash 696a966bdf37, 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.

src/skills_builtin/api-design/SKILL.md · 28 lines

What it actually says

An API (a function, module, endpoint, or library surface) is a contract others depend on. Design the smallest, clearest one that does the job.

  1. Start from the caller. Write the usage you wish existed first. If it reads well and the obvious call is the correct one, the design is good.
  2. Make it hard to misuse. Prefer types/enums over stringly-typed flags; make illegal states unrepresentable; require the essential args, default the rest. The easy path should be the safe path.
  3. Keep the surface small. Expose the minimum; hide internals. Every public name is a future maintenance promise. Fewer, well-named entry points beat many overlapping ones.
  4. Be consistent. Match the naming, argument order, and error conventions of the surrounding code so callers can predict it.
  5. Define the contract: inputs, outputs, errors/failure modes, and side effects. Decide how errors surface (exception vs result) and be uniform.
  6. Design for change. Additive evolution (new optional params, new functions) over breaking signatures. If you must break, version it and migrate (see database-migrations / breaking-change discipline).
  7. YAGNI. Don't add parameters or extension points "just in case" — they're surface you'll maintain forever. Add them when a real caller needs them.
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 · 28 lines · 17 tokens per session scan A 696a966bdf37

Subscribe to this mod's changes

api-design is a skill published in the GitHub repository New1Direction/korgex (5 stars, last pushed 2mo ago), licensed MIT. It adds 17 tokens to every session and 345 once invoked, about $0.0001 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 2026-08-31.