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

Annotations already declare readOnlyHint, so the safe-read behavior is covered. The description adds useful context by listing return facets and noting the operation is 'Free', but it does not explain any limits, output structure, or why sheet.asset_id should be preferred.

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?

The description is extremely short and contains no filler; every fragment adds information. It is telegraphic to the point of being cryptic, but each item (entity scope, facets, ref preference, cost) earns its place.

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?

For a one-parameter read-only tool this is mostly adequate: it names the return facets and gives an id preference. Still, without an output schema, the description leaves ambiguity about the exact return format, what refs are accepted, and whether sheet.asset_id is required or merely preferred.

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?

The schema has zero description coverage for the single id parameter, so the description carries the full burden. 'Prefer sheet.asset_id as a ref' is a valuable, concrete hint about what kind of identifier to pass, partially compensating for the otherwise bare string type.

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?

The title ('One character, prop or place') plus description ('One entity: refs, sheet, looks, links, facets, bio, voice') makes clear this retrieves a single entity of a certain type and lists the data facets it returns. However, it never states the action explicitly and does not distinguish itself from sibling tools like get_asset or list_entities.

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?

The only usage hint is 'prefer sheet.asset_id as a ref', which addresses how to form the id parameter but not when to choose this tool over alternatives. No context is given for when get_entity is appropriate versus list_entities or get_asset.

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