M11 Ecosystem Agent Skill

Current Dependencies (Auto-Injected)

!grep -A 100 '^\[dependencies\]' Cargo.toml 2>/dev/null | head -30 || echo "No Cargo.toml found"

Ecosystem Integration

> Layer 2: Design Choices

Core Question

What's the right crate for this job, and how should it integrate?

Before adding dependencies:

• Is there a standard solution?
• What's the maintenance status?
• What's the API stability?

Integration Decision → Implementation

| Need | Choice | Crates |

|------|--------|--------|

| Serialization | Derive-based | serde, serde_json |

| Async runtime | tokio or async-std | tokio (most popular) |

| HTTP client | Ergonomic | reqwest |

| HTTP server | Modern | axum, actix-web |

| Database | SQL or ORM | sqlx, diesel |

| CLI parsing | Derive-based | clap |

| Error handling | App vs lib | anyhow, thiserror |

| Logging | Facade | tracing, log |

Thinking Prompt

Before adding a dependency:

• Is it well-maintained?
• Recent commits?
• Active issue response?
• Breaking changes frequency?

• What's the scope?
• Do you need the full crate or just a feature?
• Can feature flags reduce bloat?

• How does it integrate?
• Trait-based or concrete types?
• Sync or async?
• What bounds does it require?

Trace Up ↑

To domain constraints (Layer 3):

"Which HTTP framework should I use?"
    ↑ Ask: What are the performance requirements?
    ↑ Check: domain-web (latency, throughput needs)
    ↑ Check: Team expertise (familiarity with framework)

| Question | Trace To | Ask |

|----------|----------|-----|

| Framework choice | domain-* | What constraints matter? |

| Library vs build | domain-* | What's the deployment model? |

| API design | domain-* | Who are the consumers? |

Trace Down ↓

To implementation (Layer 1):

"Integrate external crate"
    ↓ m04-zero-cost: Trait bounds and generics
    ↓ m06-error-handling: Error type compatibility

"FFI integration"
    ↓ unsafe-checker: Safety requirements
    ↓ m12-lifecycle: Resource cleanup

Quick Reference

Language Interop

| Integration | Crate/Tool | Use Case |

|-------------|------------|----------|

| C/C++ → Rust | bindgen | Auto-generate bindings |

| Rust → C | cbindgen | Export C headers |

| Python ↔ Rust | pyo3 | Python extensions |

| Node.js ↔ Rust | napi-rs | Node addons |

| WebAssembly | wasm-bindgen | Browser/WASI |

Cargo Features

| Feature | Purpose |

|---------|---------|

| [features] | Optional functionality |

| default = [...] | Default features |

| feature = "serde" | Conditional deps |

| [workspace] | Multi-crate projects |

Error Code Reference

| Error | Cause | Fix |

|-------|-------|-----|

| E0433 | Can't find crate | Add to Cargo.toml |

| E0603 | Private item | Check crate docs |

| Feature not enabled | Optional feature | Enable in features |

| Version conflict | Incompatible deps | cargo update or pin |

| Duplicate types | Different crate versions | Unify in workspace |

Crate Selection Criteria

| Criterion | Good Sign | Warning Sign |

|-----------|-----------|--------------|

| Maintenance | Recent commits | Years inactive |

| Community | Active issues/PRs | No response |

| Documentation | Examples, API docs | Minimal docs |

| Stability | Semantic versioning | Frequent breaking |

| Dependencies | Minimal, well-known | Heavy, obscure |

Anti-Patterns

| Anti-Pattern | Why Bad | Better |

|--------------|---------|--------|

| extern crate | Outdated (2018+) | Just use |

| #[macro_use] | Global pollution | Explicit import |

| Wildcard deps * | Unpredictable | Specific versions |

| Too many deps | Supply chain risk | Evaluate necessity |

| Vendoring everything | Maintenance burden | Trust crates.io |

Related Skills

| When | See |

|------|-----|

| Error type design | m06-error-handling |

| Trait integration | m04-zero-cost |

| FFI safety | unsafe-checker |

| Resource management | m12-lifecycle |