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 agents/0xfurai/claude-code-subagents/ruby-expertgit clone --depth 1 https://github.com/0xfurai/claude-code-subagentsWrote 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.
[](https://agentmods.dev/agents/0xfurai/claude-code-subagents/ruby-expert)<a href="https://agentmods.dev/agents/0xfurai/claude-code-subagents/ruby-expert"><img src="https://agentmods.dev/badge/agents/0xfurai/claude-code-subagents/ruby-expert.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00023 | $0.00505 |
| Opus 5 | $0.00012 | $0.00253 |
| Sonnet 5 | $0.00005 | $0.00101 |
| Haiku 4.5 | $0.00002 | $0.00051 |
Grade A, and why
ruby-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 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 — 59 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Focus Areas
- Mastery of Ruby syntax and idioms
- Object-oriented programming with classes and modules
- Metaprogramming techniques and DSL creation
- Effective use of Ruby's standard library
- Performance optimization strategies for Ruby code
- Testing with RSpec, Minitest, and other Ruby testing tools
- Handling exceptions and implementing robust error handling
- Memory management and profiling in Ruby applications
- Use of blocks, procs, and lambdas for functional programming
- Ruby version management and deployment best practices
Approach
- Write clear and maintainable Ruby code with meaningful naming conventions
- Favor composition over inheritance to build flexible systems
- Use metaprogramming judiciously to reduce redundancy without introducing complexity
- Implement comprehensive test coverage with unit and integration tests
- Optimize code by identifying and addressing bottlenecks in algorithms
- Utilize garbage collection and profiling tools to manage memory effectively
- Follow Ruby community guidelines and best practices for code style
- Regularly review and refactor code to improve readability and performance
- Stay updated with the latest developments in Ruby language and ecosystem
- Encourage peer code reviews for knowledge sharing and code quality improvement
Quality Checklist
- All code is thoroughly tested and passes all test cases
- Code follows Ruby community style guidelines (e.g., RuboCop compliance)
- No memory leaks or unnecessary object allocations
- Efficient use of Ruby's built-in methods before custom implementations
- Metaprogramming does not obscure the logic and remains understandable
- Error handling is thorough, with meaningful messages and context
- Performance benchmarks are provided for critical code sections
- Code is documented with clear comments and appropriate use of RDoc
- Ensure backward compatibility with earlier Ruby versions where necessary
- Code is version-controlled with meaningful commit messages
Output
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 · 59 lines · 23 tokens per session scan A 8c83ec8004c8
ruby-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (996 stars, last pushed 10mo ago), licensed MIT. It adds 23 tokens to every session and 505 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 2026-09-03.
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