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 rules/tyrchen/cursor-rust-rules/maingit clone --depth 1 https://github.com/tyrchen/cursor-rust-rulesWhat 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 | $0.00000 | $0.03926 |
| Opus 5 | $0.00000 | $0.01963 |
| Sonnet 5 | $0.00000 | $0.00785 |
| Haiku 4.5 | $0.00000 | $0.00393 |
Grade A, and why
main 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 — 416 lines — stays where its author put it; the contents beside it link to each section on GitHub.
🦀 RUST PROJECT RULE SET SYSTEM
TL;DR: This system provides comprehensive guidelines for Rust project development with complexity-based rule loading, following industry best practices for scalable, maintainable Rust code.
🔍 PROJECT COMPLEXITY DETERMINATION
graph TD
Start["New Rust Project"] --> Analyze["Analyze Project Requirements"]
Analyze --> Q1{"Multiple distinct<br>functional domains?"}
Q1 -->|Yes| Q2{"Expected LOC<br>> 10,000?"}
Q1 -->|No| Q3{"Single domain with<br>multiple components?"}
Q2 -->|Yes| Complex["COMPLEX PROJECT<br>Multi-crate workspace"]
Q2 -->|No| Q4{"Shared libraries<br>needed?"}
Q4 -->|Yes| Complex
Q4 -->|No| Simple["SIMPLE PROJECT<br>Single crate"]
Q3 -->|Yes| Q5{"Need separate<br>deployable units?"}
Q3 -->|No| Simple
Q5 -->|Yes| Complex
Q5 -->|No| Simple
Complex --> LoadComplex["Load Complex Rules"]
Simple --> LoadSimple["Load Simple Rules"]
LoadComplex --> Features["Load Feature-Specific Rules"]
LoadSimple --> Features
Features --> Web{"Web Framework<br>needed?"}
Features --> DB{"Database<br>access needed?"}
Features --> CLI{"CLI interface<br>needed?"}
Features --> GRPC{"gRPC/Protobuf<br>needed?"}
Features --> Concurrent{"Heavy<br>concurrency?"}
Features --> Config{"Complex config<br>or templating?"}
Features --> Observability{"Metrics & tracing<br>needed?"}
Features --> ConfigMgmt{"Dynamic config<br>management?"}
Web -->|Yes| WebRules["Load Axum Rules"]
DB -->|Yes| DBRules["Load Database Rules"]
CLI -->|Yes| CLIRules["Load CLI Rules"]
GRPC -->|Yes| GRPCRules["Load Protobuf & gRPC Rules"]
Concurrent -->|Yes| ConcurrencyRules["Load Concurrency Rules"]
Config -->|Yes| ToolsRules["Load Tools & Config Rules"]
Observability -->|Yes| ObservabilityRules["Load Observability Rules"]
ConfigMgmt -->|Yes| ConfigMgmtRules["Load Configuration Rules"]
style Start fill:#4da6ff,stroke:#0066cc,color:white
style Complex fill:#d94dbb,stroke:#a3378a,color:white
style Simple fill:#4dbb5f,stroke:#36873f,color:white
style LoadComplex fill:#ffa64d,stroke:#cc7a30,color:white
style LoadSimple fill:#4dbbbb,stroke:#368787,color:white
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 · 416 lines · 0 tokens per session scan A 77fc36acafe3
main is a cursor rule published in the GitHub repository tyrchen/cursor-rust-rules (27 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 3,926 tokens. 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 2026-08-30.
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