Ensure that similar APIs follow consistent patterns and conventions across the codebase. When designing or modifying APIs, maintain the same expressivity, return type patterns, and usage conventions as existing similar APIs.

Key areas to check:

Example from the codebase:

// Inconsistent - mixing different return patterns
function someApi(): ValidationError | ValidationError[] // inconsistent with other APIs

// Consistent - following established OneOrMany pattern  
function someApi(): OneOrMany<ValidationError> // matches other similar APIs

// Inconsistent - different creation patterns
new ReactiveMetadataKey() vs MetadataKey.someFactory()

// Consistent - uniform factory pattern
MetadataKey.reduce() // always use static factories

This helps users build intuitive mental models and reduces cognitive load when working with related APIs.