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

No annotations are present, so the description carries the burden. It discloses the data source (Rakuten), update cadence (daily), and normalization basis, which is useful behavioral context. However, it does not mention the response shape, pagination, or error behavior, and it does not explicitly state that the operation is a read-only lookup.

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 meaning (daily unit prices of daily necessities) comes first, followed by parameter guidance and a pointer to the index tool. Nothing is filler, though the single run-on sentence could be slightly better structured.

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 read tool with no output schema and no annotations, the description covers source, frequency, normalization, slug examples, and the sibling index tool. It does not describe the return format, but that is a minor omission given the low complexity and clear data semantics.

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?

With 0% schema description coverage, the description compensates by giving concrete slug values (toilet-paper, tissue, diaper-pants, laundry-detergent, water, rice) and directing the agent to nichiyo_index for the full list. It does not exhaustively enumerate valid slugs or specify slug format rules, but for a single required parameter this is sufficient guidance.

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 clearly identifies the tool as a daily listing of unit prices for daily necessities from Rakuten, normalized to per-roll/per-sheet/100ml/per-kg. It is unambiguous about the resource, though it does not explicitly contrast with other price-related siblings such as cheapest or hikaku; it only points to nichiyo_index for the broader list.

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 implies when to use the tool: when you need unit prices for daily necessities identified by a slug, with example slugs provided. It also tells the agent to use nichiyo_index for the catalog/list, which is a form of alternative routing, but it gives no explicit conditions for avoiding this tool or choosing among the many sibling price tools.

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