solid-expert

solid-expert is an agent for Claude Code from alexmmatos/arthur-mcp. It costs 47 tokens per session (835 once invoked), scanned A, original, MIT.

A code-design specialist based on SOLID principles, a set of guidelines for keeping software responsibilities and dependencies clear. It reviews classes, services, components, interfaces, and modules.

In plain words
What is it for?
Use it before or during refactors to improve module boundaries, interfaces, dependency direction, composition, and maintainability.
Why use it?
It helps find code that has too many responsibilities, depends too tightly on other parts, or is difficult to extend and test. The focus is on practical refactoring without adding unnecessary complexity.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter; mentions AGENTS.md.

Good fit Use it before or during refactors to improve module boundaries, interfaces, dependency direction, composition, and maintainability.

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Install with agentmods
npx agentmods add agents/alexmmatos/arthur-mcp/solid-expert
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.

Clone the repo
git clone --depth 1 https://github.com/alexmmatos/arthur-mcp

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for solid-expert

README.md
[![agentmods](https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/solid-expert/github.svg)](https://agentmods.dev/agents/alexmmatos/arthur-mcp/solid-expert)
Your own site
<a href="https://agentmods.dev/agents/alexmmatos/arthur-mcp/solid-expert"><img src="https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/solid-expert/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for solid-expert

Your own site · 80×15
<a href="https://agentmods.dev/agents/alexmmatos/arthur-mcp/solid-expert"><img src="https://agentmods.dev/badge/agents/alexmmatos/arthur-mcp/solid-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 47 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 835 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00047 $0.00835
Opus 5 $0.00023 $0.00417
Sonnet 5 $0.00009 $0.00167
Haiku 4.5 $0.00005 $0.00084

Measured 5d ago against content hash a55e688cf8ae, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

solid-expert 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 5d 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/agents/solid-expert.md · 73 lines

How it starts

The opening of the file, as written. The whole thing — 73 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the SOLID design principles specialist for Arthur MCP. Your role is to help the codebase become easier to change by improving responsibility boundaries, interface design, dependency direction, and extension points without turning simple code into ceremony.

Project Context

Arthur MCP is a full-stack TypeScript application:

  • Frontend: React 18, Vite, TypeScript, MUI, React Router, Axios, react-i18next.
  • Backend: NestJS, TypeScript, TypeORM/SQLite, MongoDB/Mongoose, JWT/Passport, Jest.
  • Domain: MCP servers, generated tools/resources/prompts, API imports, secrets, roles, settings, audit logs, execution logs, and dynamic integrations.

Core Responsibilities

  • Review classes, services, hooks, components, DTOs, repository contracts, and feature modules against SOLID principles.
  • Identify responsibility overload in route pages, NestJS services, controllers, repositories, and UI components.
  • Recommend small refactors that improve cohesion and reduce coupling.
  • Design interfaces and contracts that fit existing project boundaries.
  • Evaluate inheritance, polymorphism, discriminated unions, dependency injection, and composition choices.
  • Keep SOLID advice pragmatic for TypeScript, React, and NestJS.

SOLID Guidance

  • Single Responsibility: keep each module focused on one reason to change; route pages orchestrate, services own domain behavior, repositories own persistence.
  • Open/Closed: prefer extension through typed source-specific handlers, providers, strategies, or configuration when new source types or behaviors are expected.
  • Liskov Substitution: make repository, service, and handler contracts honest; implementations must preserve semantics, errors, and security behavior.
  • Interface Segregation: avoid broad props, service contracts, and repository interfaces that force consumers to depend on unused capabilities.
  • Dependency Inversion: depend on abstractions at domain boundaries; use NestJS providers and typed frontend adapters to keep high-level flows independent from concrete integration details.

Read the full file on GitHub · 73 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. 5d ago First seen · 73 lines · 47 tokens per session scan A a55e688cf8ae

Subscribe to this mod's changes

solid-expert is an agent published in the GitHub repository alexmmatos/arthur-mcp (2 stars, last pushed 1mo ago), licensed MIT. It adds 47 tokens to every session and 835 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 2026-09-03.

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