Use this agent when new features introduce new nouns or entities that need to be validated against the existing domain model. Use it when confusion exists between similar concepts and clarification is needed. Use it before schema or protocol changes to ensure naming consistency. Use it when naming feels inconsistent across code, database schemas, protocol docs, or UI language. Use it when reviewing feature proposals that might accidentally introduce duplicate or overlapping concepts.\n\nExamples:\n\n<example>\nContext: A developer is proposing a new feature that introduces a 'StickerTemplate' concept.\nuser: "I'm adding a new feature for sticker templates. Users can save stickers as templates to reuse later. I'm calling it StickerTemplate."\nassistant: "Let me use the entities-librarian agent to validate this new entity against our existing domain model and ensure it doesn't overlap with existing concepts."\n<commentary>\nSince a new noun/entity is being introduced, use the entities-librarian agent to validate the concept, check for overlaps with existing entities like Sticker, Asset, or WidgetType, and provide clear boundary definitions.\n</commentary>\n</example>\n\n<example>\nContext: A team member is confused about the difference between CanvasItem and WidgetInstance.\nuser: "I'm not sure when to use CanvasItem vs WidgetInstance. They seem similar - can you clarify?"\nassistant: "I'll use the entities-librarian agent to provide authoritative clarification on these domain entities and their distinct responsibilities."\n<commentary>\nSince confusion exists between similar concepts, use the entities-librarian agent to provide clear definitions and boundaries between CanvasItem and WidgetInstance.\n</commentary>\n</example>\n\n<example>\nContext: A developer notices inconsistent naming in a PR.\nuser: "In this PR, we're calling it 'gallery_entry' in the database but 'GalleryItem' in the code and 'Gallery Card' in the UI. Is this right?"\nassistant: "Let me consult the entities-librarian agent to check our canonical naming conventions and identify if there's inconsistency that needs to be addressed."\n<commentary>\nSince naming inconsistency is detected across database, code, and UI, use the entities-librarian agent to provide authoritative guidance on correct naming.\n</commentary>\n</example>\n\n<example>\nContext: Before a schema migration that adds new fields.\nuser: "We're planning a database migration to add a 'thumbnail' field. Should it go on Asset or on Sticker?"\nassistant: "I'll use the entities-librarian agent to analyze the entity boundaries and provide guidance on where this field belongs based on our domain model."\n<commentary>\nSince this is a schema change that affects entity definitions, use the entities-librarian agent to ensure the change respects entity boundaries and responsibilities.\n</commentary>\n</example>