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

With no annotations, the description carries the full disclosure burden, and it does add real behavioral context: a metered cost of $0.005 USDC per call via x402 (_meta["x402/payment"]) and a free 3-row preview. The data provenance (Ministry of Health, Labour and Welfare FY2024 DPC) is also useful for trust. It stops short of describing return shapes, pagination totals, or error behavior for invalid route placeholders.

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 purpose and data provenance are front-loaded, and the dense route/parameter enumeration is information-bearing rather than padding. The route list is duplicated verbatim in the input schema's `route` description, which is minor waste. The whole definition is one paragraph, appropriate for a router-style tool.

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 17-route meta-API with no output schema, the description covers how to call it (routes, per-route params, pricing, free preview) but not what comes back. An agent can invoke it yet cannot predict the response shape of /summary versus /prefectures/{pref}/health-profile, which matters when choosing a route. That leaves a meaningful gap relative to the tool's complexity.

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 schema already documents route, params, and sample. The description adds meaningful detail by mapping accepted query parameters to individual routes (e.g. /hospitals accepts pref, q, city_code, dpc_status, min_beds, max_beds, mdc, min_cases, sort, limit, offset), which the schema's free-form `params` object cannot convey. Because parameter semantics are only implied and never defined, the baseline 3 is right.

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?

Names the resource precisely: "Japan Hospitals and Prefecture Health Facts", sourced from the MHLW FY2024 DPC discharge-patient survey. The route list makes the coverage concrete. It does not, however, distinguish itself from sibling tools such as `japan` or `regions`, so an agent must infer the boundary from the subject matter alone.

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?

There is no when-to-use guidance: nothing explains what /gaps returns versus /rank versus /mdc, or which route answers which question. The only selection aid is the sample=true free preview, which is a cost-control hint rather than usage guidance. The agent must guess route semantics from names like "gaps" and "rank".

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