#Types

Annotations describe a valid value; validation establishes whether an external value belongs to that type.

#Validated models

#Why

A type annotation does not validate decoded JSON or an external SDK response at runtime.

#Rules

• MUST receive untrusted values as object until runtime checks validate them. [review]

• MUST avoid Any, unchecked casts, and type-ignore directives that bypass validation. [review]

• MUST represent closed alternatives with typed unions, literals, or enums. [review]

• MUST use frozen records with immutable fields for domain models. [review]

• MUST distinguish absent values from failures that require an explanation. [review]

• MUST use Protocols for injected capabilities when structural typing is needed. [review]

• MUST retain explicit generic Result annotations so error types do not degrade into Any. [review]

• MUST verify the returns decorator/composition types with its supported mypy plugin. [review]

[review]

Strict typechecks verify annotations and supported plugin inference. Boundary tests verify runtime validation.

#Enforcement

Strict typechecks verify annotations and supported plugin inference. Boundary tests verify runtime validation.