Use when integrating crates or ecosystem questions. Keywords: E0425, E0433, E0603, crate, cargo, dependency, feature flag, workspace, which crate to use, using external C libraries, creating Python extensions, PyO3, wasm, WebAssembly, bindgen, cbindgen, napi-rs, cannot find, private, crate recommend

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: 1. Is it well maintained? Recent commits? Active issue response? Breaking changes frequency? 2. What's the scope? Do you need the full crate or just a feature? Can feature flags reduce bloat? 3. How does it integrate? Trait based or concrete types? Sync or async? What bounds does it require? Trace Up ↑ To domain constraints (Layer 3): 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): 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

m11-ecosystem