Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely useful non-obvious context: it renders an interactive UI in the conversation and emits a fallback text summary plus link for non-UI clients. Minor gap: it doesn't say what happens if the slug or chapter id is invalid.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads what the tool does before the usage rule and the fallback behavior. The first sentence carries several clauses but each conveys distinct information. Slightly dense, but no sentence is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description must cover returns — and it does, stating it yields a short text summary and the plate's link. Combined with the read-only annotation profile and full schema coverage, an agent has everything needed to call this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so every parameter including nested params and lab already has a description. The description reinforces provenance ('with the slug and chapter (and params) it returned'), but adds no syntax or format detail beyond the schema. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Shows one interactive 3D model from world.lapla.si') plus its interaction model (turn, step through chapters, try the lab). It is clearly distinguishable from siblings search_models and list_chapters, which it explicitly positions itself after.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit trigger conditions: 'Use it after search_models with the slug and chapter (and params) it returned, or when the user names a plate.' This names both the upstream dependency and an independent trigger, leaving nothing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.