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

With no annotations, the description carries the full burden and does so well: it discloses the payment model ($0.05 USDC per call via x402 _meta["x402/payment"]), the free sample escape hatch, the data provenance (official figures, no personal data), and the coverage window. It does not mention rate limits, failure modes, or latency, which keeps it from 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?

It is dense but well front-loaded: value proposition first, then scope, then returned metrics, then routes and pricing. Every clause carries information, though the route and pricing details are packed into a single run-on final sentence that could be broken up for easier scanning.

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, nested-parameter, paid tool with no output schema, the description covers the essentials: what data exists, what the return metrics are (net, net share of local tax, growth, rank, verdict), how to address each route, and how billing and the free preview behave. Only edge cases like invalid codes or pagination behavior are left unstated.

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 earns more because the schema's route field is generic boilerplate ('Replace {placeholders}... e.g. /search or /HND') and never enumerates the actual query keys. The description supplies the real per-route parameters: /top (by, year, limit); /city (code); /answer (name, pref, code), which the schema alone would not convey.

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 names a specific domain (furusato nozei / hometown tax) and a specific analytical output (net gain/loss per municipality), with exact scope: 1,741 municipalities, fiscal years 2015-2025. It is clearly distinguishable from siblings like jp-health, jp-household, and local-markets because it says precisely which fiscal flow it measures.

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?

It distinguishes the two usage modes well: one town with rank and verdict versus a ranked list of top towns, and it explicitly says to set sample=true for a free 3-row preview before paying. It does not state when to prefer a sibling tool or when this tool is not appropriate, so it falls short of a full 5.

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