How do modules handle inputs, outputs, locals and validation effectively?

Define typed variables with defaults and validation blocks to guard against invalid CIDRs, AZ counts, or empty strings.

Use locals to transform data or derive names, and combine with for_each/count for deterministic resource creation.

Document outputs in outputs.tf, mark sensitive ones, and keep outputs minimal to reduce coupling.

Surface module metadata (like version or tags) through outputs for downstream modules or automation.