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

Goes well beyond the readOnly/openWorld annotations: declares the per-call price ($0.002 USDC via x402 on Base/Solana/Arc), that failed calls are not billed, that results are 30 per page, and that all text is Japanese as published. Cost and billing behavior in particular are information the agent cannot get from the schema.

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?

Front-loaded with source and subject, and the pricing sentence is separated out where it belongs. The field enumeration is long but each item earns its place by telling the agent what it will get back; only slightly dense as a single run-on list.

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?

Output schema, annotations and full schema coverage already carry a lot, yet the description still supplies the non-structural essentials: source, language of returned text, page size, field contents and billing model. Nothing an agent needs before calling is missing.

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 the meaningful detail that each page holds 30 results, which directly informs how to interpret the 'page' parameter (1–50). It otherwise mirrors the schema's prefecture/ward explanations without adding syntax.

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/resource ('Second-hand condominiums for sale in Japan from SUUMO') and even enumerates the returned fields, which cleanly separates it from the mostly non-Japan real-estate siblings. An agent knows immediately what this retrieves and from which source.

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 geographic and category scope ('Japan', 'second-hand condominiums', SUUMO) gives clear context for when this tool applies, and 'for a prefecture (and optionally a city/ward code)' indicates the required narrowing. It stops short of naming alternatives or exclusions (e.g. rentals, new builds), so it is a 4 rather than a 5.

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