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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety burden is lifted. The description adds real behavioral context by disclosing the payload's scope (hierarchy boundaries, unit, covered period) versus quantitative figures, which steers correct tool choice. It stops short of stating behavior for unknown/invalid codes or whether child listings are exhaustive.

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 substantive content is front-loaded and short, but the English half repeats the navigation clause twice ('Use this to navigate the hierarchy' / 'use this to navigate parent and child levels'), and the entire text is then duplicated in Japanese. The bilingual pairing is defensible given the lang parameter, yet the redundant clause wastes attention.

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 4-parameter read tool with no output schema, the description still sketches the return payload (hierarchy levels, unit, months covered) and routes to get_item_summary for figures. Only edge behavior (invalid code, missing level) is left unaddressed, which the schema partially covers.

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 description coverage is 100%, with enum descriptions for flow, lang and level, and the code parameter already points to search_items for lookup. The description adds nothing beyond the schema about how code, flow or level interact (e.g., level inference from code length is only in the schema). Baseline 3 applies when the schema does the heavy lifting.

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 resource and its returned content: 'Item details: parent and child levels, unit, and the months covered.' It also explicitly separates itself from the sibling get_item_summary ('For an item's figures, partners and growth, use get_item_summary'), so an agent can distinguish the two without opening either schema.

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 both the when ('use this to navigate parent and child levels') and the when-not with a named alternative ('For an item's figures, partners and growth, use get_item_summary'). The routing decision is fully specified rather than implied.

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