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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, and the description adds meaningful context beyond them: the data source (MLIT), the curated coverage limit (919 filings across 75 popular JDM models), that returned text is Japanese-original, and that a filing PDF is included. The coverage cap is exactly the kind of constraint an agent needs to judge result completeness.

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?

Two sentences, front-loaded with the resource and source, then the input-language flexibility. Dense but each clause carries information; the parenthetical statistics are slightly heavy but earn their place as coverage constraints.

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?

With no output schema, the description compensates by listing the returned fields (notification number, date, defective device, affected vehicles, situation, remedy, PDF). Minor gaps remain: no indication of result volume, pagination, or behaviour when a make/model has no matched filings.

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 the baseline is 3; the description adds real value by stating that both English ('Toyota Prius') and Japanese ('トヨタ プリウス') inputs are accepted, which the schema only hints at via examples. It does not clarify matching behavior (e.g. partial vs exact, case handling).

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 — retrieving official Japanese recall filings for a given make and model — and enumerates the returned fields. The geographic and domain scope ('国土交通省 MLIT') cleanly separates it from the fr_*, uk_* and eu_* recall siblings.

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 'for a make and model' framing and the JP-specific scope make it obvious when to pick this over fr_recalls_for_model or uk_recalls_for_model. It does not, however, give explicit when-not guidance or mention the related jp_complaints_summary alternative.

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