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

With no annotations, the description carries the full burden and does disclose two high-value behaviors: a paid $0.005 USDC cost per call via x402 (_meta["x402/payment"]) and a free sample=true 3-row preview. It omits what happens on payment failure, whether unauthenticated calls error, and the response shape, keeping it short of a 5.

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 critical facts — what the data is, the routes, the price, the free preview — are front-loaded in one dense paragraph with no repeated sentences. The 'for real-estate tools, relocation apps, local-business dashboards and AI agents' clause is marketing filler that does not help the agent act.

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 multi-route gateway with nested params and no output schema, the description does the important work: it names all four routes with their parameters and discloses cost plus the free preview escape hatch. The main residual gap is that nothing describes the returned payload or pagination semantics, which matters more here since no output schema exists.

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, but the description goes further by enumerating each route's accepted query parameters (indicator*, year, prefecture, order, limit, offset; q for /municipalities; indicator for /municipalities/{code}) and marking indicator as required with an asterisk. It still leaves the meaning of indicator codes and limit/offset defaults unexplained.

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 (official statistics for every Japanese municipality) delivered as a JSON API, which clearly separates it from the dataset-oriented siblings like airports, colors, or power. It does not explicitly contrast itself with any sibling, but the dataset subject is unambiguous.

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 route list implies which endpoint to call for ranking, indicator listing, municipality search, or single-municipality lookup, which is useful implied guidance. However, nothing states when to use /rank versus /municipalities, what an 'indicator' is, or any exclusions, so the agent must infer the routing decision.

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