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.
npx agentmods add skills/helmedeiros/clean-code-skills/solid-interface-segregationnpx skills add helmedeiros/clean-code-skills --skill solid-interface-segregationgit clone --depth 1 https://github.com/helmedeiros/clean-code-skillsWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00048 | $0.00676 |
| Opus 5 | $0.00024 | $0.00338 |
| Sonnet 5 | $0.00010 | $0.00135 |
| Haiku 4.5 | $0.00005 | $0.00068 |
Grade A, and why
solid-interface-segregation 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.
How it starts
The opening of the file, as written. The whole thing — 76 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SOLID: Interface Segregation Principle
Design small, focused interfaces so that clients depend only on the methods they actually use, avoiding forced dependencies on irrelevant functionality.
When This Skill Applies
- An interface has methods that some implementors leave empty or throw NotImplementedException
- Clients import an interface but only call a subset of its methods
- The user mentions ISP, interface segregation, or fat interfaces
- Changing one interface method forces recompilation or retesting of unrelated clients
- Mock objects in tests implement many methods just to satisfy the interface
Core Principle
No client should be forced to depend on methods it does not use. Large, general-purpose interfaces create coupling between unrelated clients. When one client needs a change to the interface, other clients are affected even though they do not use the changed method. Split fat interfaces into smaller, role-specific ones.
Workflow
Step 1: Identify the Fat Interface
Find interfaces with many methods where different clients use different subsets. Look for implementors that leave methods empty or throw exceptions.
Step 2: Group Methods by Client
Identify which clients call which methods. Group methods that are always used together. Each group becomes a candidate for a separate interface.
Step 3: Define Role Interfaces
Create a focused interface for each group. Name each interface after the role it represents: Readable, Writable, Closeable instead of one FileOperations.
Step 4: Update Implementors
Classes that previously implemented the fat interface now implement the specific role interfaces they support. A class can implement multiple interfaces.
Step 5: Update Clients
Each client depends on the smallest interface that covers its needs. Update parameter types and dependency declarations.
Detection / Indicators
- Interface with more than 5-7 methods
- Implementors with empty method bodies or
throw new NotImplementedException() - Tests that mock many methods but only exercise one
- Clients that import an interface but call only 1-2 methods
- Interface changes that cause unrelated code to recompile
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 76 lines · 48 tokens per session scan A 436d7ec5a39a
solid-interface-segregation is a skill published in the GitHub repository helmedeiros/clean-code-skills (2 stars, last pushed 6mo ago), licensed MIT. It adds 48 tokens to every session and 676 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 2026-08-31.
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