isp

A guide for fixing Interface Segregation Principle problems. This principle says that a class should not be forced to support interface methods it does not need; an interface is a defined set of operations that code promises to provide.

In plain words
What is it for?
Use it with the /isp command to inspect a file or changed files, identify overly broad interfaces, and apply a confirmed fix with a summary of the differences.
Why use it?
It helps find oversized interfaces that make implementations carry unused or unsupported methods. It checks selected files and reports the proposed change for confirmation.

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/muthuspark/solid-audit/isp
Any agent
npx skills add muthuspark/solid-audit --skill isp
Clone the repo
git clone --depth 1 https://github.com/muthuspark/solid-audit

Made for: Claude Code, Codex.

Per session 15 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,988 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 $0.00015 $0.01988
Opus 5 $0.00008 $0.00994
Sonnet 5 $0.00003 $0.00398
Haiku 4.5 $0.00002 $0.00199

Measured yesterday against content hash d8050677224f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

isp 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 yesterday.

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.

solid-audit/skills/isp/SKILL.md · 235 lines

How it starts

The opening of the file, as written. The whole thing — 235 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Trigger

This skill activates when the user runs /isp (optionally with a file path argument, e.g. /isp src/interfaces/worker.py).

Scope Detection

Determine which files to analyze using this priority order:

  1. Argument — If the user provided a file or directory path after /isp, use that directly.
  2. Git staged — Run git diff --cached --name-only. If output is non-empty, use those files.
  3. Git unstaged — Run git diff --name-only. If output is non-empty, use those files.
  4. Ask user — If no git diff is available, ask for a file or directory path.

Always skip: *.lock, package-lock.json, yarn.lock, pnpm-lock.yaml, Gemfile.lock, composer.lock, **/migrations/**, **/__generated__/**, **/fixtures/**, **/*.min.js

ISP Fix Logic

Detection

An interface/ABC violates ISP when it forces implementors to provide methods they don't actually use. Look for:

  1. Fat ABC/Protocol/interface:

    • Python: abc.ABC or typing.Protocol with 6+ abstract methods where a concrete implementor stubs ≥ half with pass or raise NotImplementedError
    • TypeScript: interface with 6+ methods where an implementing class throws new Error("not supported") for multiple methods
    • Java: interface with multiple methods where an implementing class throws UnsupportedOperationException
    • Go: interface type that is larger than what any single caller actually needs
    • C#: interface with multiple methods where a class throws NotImplementedException
    • Kotlin: interface with multiple methods where a class uses TODO() or throws UnsupportedOperationException
    • Ruby: module with multiple methods raising NotImplementedError in classes that only use a subset
    • PHP: interface with multiple methods where a class throws BadMethodCallException
  2. Mixed responsibilities in one interface: The interface has methods from two or more logically distinct domains (e.g., both print() and scan() and send_email())

Read the full file on GitHub · 235 lines

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. yesterday First seen · 235 lines · 15 tokens per session scan A d8050677224f

Subscribe to this mod's changes

isp is a skill published in the GitHub repository muthuspark/solid-audit (5 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 15 tokens to every session and 1,988 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.

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