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 skills add G1Joshi/Agent-Skills --skill crystalgit clone --depth 1 https://github.com/G1Joshi/Agent-SkillsWrote 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/skills/g1joshi/agent-skills/crystal)<a href="https://agentmods.dev/skills/g1joshi/agent-skills/crystal"><img src="https://agentmods.dev/badge/skills/g1joshi/agent-skills/crystal/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.
<a href="https://agentmods.dev/skills/g1joshi/agent-skills/crystal"><img src="https://agentmods.dev/badge/skills/g1joshi/agent-skills/crystal.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00017 | $0.00262 |
| Opus 5 | $0.00009 | $0.00131 |
| Sonnet 5 | $0.00003 | $0.00052 |
| Haiku 4.5 | $0.00002 | $0.00026 |
Grade A, and why
crystal 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 9d 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.
What it actually says
Crystal
Crystal compiles to native code (using LLVM) but looks exactly like Ruby. v1.12 continues improving Windows support and parallelism.
When to Use
- Performance sensitive Rubyists: Porting heavy Ruby scripts to Crystal for 50x speedup.
- Microservices: Low memory footprint compared to JVM/Ruby.
- CLI Tools: Fast startup and execution.
Core Concepts
Fibers
Lightweight concurrency (like Go routines). spawn { ... }.
Macros
Generate code at compile time (like Zig/Lisp).
Union Types
String | Int32. The compiler handles the branching.
Best Practices (2025)
Do:
- Use strict types in APIs: Help the compiler with
def foo(x : Int32). - Use
shards: Dependency manager. - Use
-Dpreview_mt: To test multithreading capabilities.
Don't:
- Don't use
eval: Crystal is compiled, there is no runtime eval.
References
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.
- 9d ago First seen · 45 lines · 17 tokens per session scan A 2d146ed2f7e9
crystal is a skill published in the GitHub repository G1Joshi/Agent-Skills (12 stars, last pushed 7mo ago), licensed MIT. It adds 17 tokens to every session and 262 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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