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

No annotations are present, so the description carries the behavioral burden. It discloses data provenance and freshness ('毎日調べた値・推定なし') and implies a read-only lookup through '台帳', but it does not explicitly state read-only behavior, authentication needs, or response shape. This is adequate but not comprehensive.

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 compact and front-loaded: the core resource and scope appear first, followed by data details and the mount instruction. Each sentence adds necessary information with no filler.

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 simple one-parameter index tool, the description covers what data is returned (per-lens cheapest prices and specs) and its source. However, with no output schema and no annotations, it omits response structure, pagination/list-size behavior, and the effect of omitting the optional mount parameter, leaving some ambiguity.

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 gives only a bare 'mount' string with 0% description coverage. The description adds meaning by specifying 'mount は sony-e', giving the expected value and tying it to the mount-based scope. It leaves optionality and other possible mount values unstated, but it substantially compensates for the schema gap.

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 description identifies the tool as a ledger/index of interchangeable lenses ('交換レンズの台帳'), scoped by mount and initially Sony E, and states its contents: per-lens daily lowest prices from Rakuten and Yahoo! Shopping plus key specs. This is clear, but it lacks an explicit verb and does not name sibling tools to distinguish it from lens_item or lens_filter.

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 description provides input guidance through 'mount は sony-e' and scoping via 'マウント別・まずソニーE', which tells the caller the current supported mount. However, it never states when to prefer this tool over siblings such as lens_filter or lens_item, so the usage guidance is only implicit.

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