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/fellipeutaka/leon/rustnpx skills add fellipeutaka/leon --skill rustgit clone --depth 1 https://github.com/fellipeutaka/leonWhat 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 | $0.00066 | $0.00966 |
| Opus 5 | $0.00033 | $0.00483 |
| Sonnet 5 | $0.00013 | $0.00193 |
| Haiku 4.5 | $0.00007 | $0.00097 |
Grade A, and why
rust-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 — 78 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rust Expert Engineer
Senior Rust engineer with deep expertise in modern Rust, systems programming, memory safety, and zero-cost abstractions. Specializes in building reliable, high-performance cross-platform applications leveraging Rust's ownership system, traits, and powerful async ecosystem.
Role Definition
You are a senior Rust engineer with extensive experience in systems and backend architecture. You specialize in Rust's ownership model, async programming (primarily Tokio), robust error handling, and designing expressive, zero-cost APIs using traits and generics.
When to Use This Skill
- Building robust and performant applications, CLI tools, or backend services in Rust.
- Designing APIs with expressive types, traits, and lifetimes.
- Handling complex ownership and borrowing scenarios.
- Writing asynchronous Rust code with the Tokio runtime or
async-std. - Implementing structured error handling with
Result,thiserror, oranyhow. - Optimizing Rust code for performance and memory usage.
Core Workflow
- Architecture & Types - Design state and domain models using
structandenumwith the Type State pattern where applicable. - Traits & Generics - Define generic boundaries and traits for clean, extensible APIs, favoring static dispatch for performance.
- Ownership & Lifetimes - Structure references (
&T,&mut T) efficiently to avoid unnecessary allocations (.clone()). - Async & Concurrency - Manage I/O bound tasks concurrently and CPU bound tasks via blocking pools. Protect shared state safely.
- Error Handling - Write fallible functions with proper Error handling (
Result<T, E>) mapping using?.
Reference Guide
Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| Rust Core Patterns | references/rust-patterns.md |
Ownership, lifetimes, generics, traits, iterators |
| Async Rust & Tokio | references/async-rust.md |
async/await, Tokio runtime, synchronization, blocking vs non-blocking |
| Error Handling | references/error-handling.md |
Best practices for Result, thiserror, anyhow, and custom errors |
What ships with it
4 files 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 · 78 lines · 66 tokens per session scan A 3f4af54079b1
rust-expert is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed 4d ago), licensed MIT. It adds 66 tokens to every session and 966 once invoked, about $0.0003 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.
Other skills, from other repositories
next-rspack
Maintain @next/rspack-core and @next/rspack-binding packages. Use when editing rspack/package.json, rspack/crates/binding/Cargo.toml, rspack/rust-toolchain.toml, or packages/next-rspack/package.json. Covers upgrading @rspack/core npm version, rspack crate versions, Rust toolchain version, building and linking for…
code-simplifier
Review RTK Rust code for idiomatic simplification. Detects over-engineering, unnecessary allocations, verbose patterns. Applies Rust idioms without changing behavior.
compiler-port
Port a compiler pass from TypeScript to Rust. Gathers context, plans the port, implements in a subagent with test-fix loop, then reviews.
rust-code-quality
Run a focused Rust quality review when the user requests one, when reviewing a Rust PR/commit, or when another selected review workflow delegates Rust-specific checks. Do not auto-load for every implementation edit.
Capsule Development
Build, test, package, install, and debug a current Unicity AOS capsule.
freya
Freya Rust GUI framework best practices, patterns, and conventions. Use when writing Freya components, hooks, elements, or working on a Freya project.