api-pattern

A method for adding an API endpoint, command handler, controller, or service by copying the established pattern in the current codebase. An API is a program interface that lets software exchange requests and results.

In plain words
What is it for?
Find the closest recent and well-tested example, study its layers and tests, then mirror its file layout, naming, validation, error handling, dependency injection, and test style when adding the new API behavior.
Why use it?
New API code can become inconsistent when each change invents its own structure, validation, errors, dependency wiring, and tests. Reusing a well-tested local example makes the new surface easier to understand and review.

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/mckruz/claude-code-sdlc/api-pattern
Any agent
npx skills add MCKRUZ/claude-code-sdlc --skill api-pattern
Clone the repo
git clone --depth 1 https://github.com/MCKRUZ/claude-code-sdlc

Made for: Claude Code, Codex.

Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 440 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 $0.00066 $0.00440
Opus 5 $0.00033 $0.00220
Sonnet 5 $0.00013 $0.00088
Haiku 4.5 $0.00007 $0.00044

Measured 2d ago against content hash 76991a60a38f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-pattern 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.

harness/skills/api-pattern/SKILL.md · 36 lines

What it actually says

API pattern

The point of this skill is consistency: the same kind of work should look the same everywhere, so reviewers and the next agent can read it without re-learning. You do not invent structure — you locate the codebase's canonical example and mirror it.

Procedure

  1. Find the canonical example. If the spec names one under "Reuse this pattern", read it. Else grep for the nearest sibling (an existing endpoint/handler of the same shape) and pick the most recent, most-tested one — not the oldest.
  2. Extract the pattern, don't paraphrase it. Note the layering (e.g. controller → MediatR command → handler → repository), the validation hook (e.g. FluentValidation auto-discovered), the error model (e.g. Result<T> vs exceptions), DI registration, and the test shape that covers it.
  3. Replicate exactly for the new surface — same naming, same file organization (one class per file), same immutability and boundary-validation conventions. Wire DI the same way.
  4. Add the matching tests in the same style as the example's tests.
  5. If the established pattern looks wrong, do not silently diverge — follow it and flag it for cleanup, or escalate. Two contradictory patterns in one codebase is a worse outcome than one imperfect-but-consistent one.

Done when

  • The new surface is indistinguishable in shape from the canonical example.
  • DI, validation, and error handling follow the same convention.
  • Tests mirror the example's test style and cover the new behavior.
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 · 36 lines · 66 tokens per session scan A 76991a60a38f

Subscribe to this mod's changes

api-pattern is a skill published in the GitHub repository MCKRUZ/claude-code-sdlc (4 stars, last pushed 4d ago), licensed MIT. It adds 66 tokens to every session and 440 once invoked, about $0.0003 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.

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