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

Annotations declare readOnlyHint=false, idempotentHint=true, and openWorldHint=true, but the description adds valuable context beyond these: it states that the tool is deterministic, cites primary sources (NTA FAQ), and that errors/unverified rules are never billed. It also discloses the $0.05/call pricing, which is not in annotations. This is meaningful behavioral information.

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 description is extremely concise at about 40 words, front-loads the core purpose, and packs in billing, determinism, and verification details without redundancy. Every sentence adds value: purpose, methodology, verification, pricing, and error policy—all in a tight, scannable format.

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 complex calculation tool with 7 parameters and no output schema, the description does not explicitly describe the return format (e.g., a breakdown of tax amounts, rates, or a report). It gives a hint via 'incremental income tax as reference' and points to /catalog for transaction spec, but the output remains underspecified. An agent would not fully know what to expect without additional assumptions.

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?

The input schema has 100% description coverage for all 7 parameters, and the tool description adds no additional parameter-level detail. The description does mention that other_taxable_income_yen returns incremental income tax as reference, but that is already in the schema. With full schema coverage, the description does not need to compensate, so baseline 3 is appropriate.

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 states a specific verb and resource ('Japan crypto-asset tax') and names the exact computation method (NTA total-average or moving-average). It clearly distinguishes this from sibling tax tools like jp_payroll_net or jp_consumption_tax by focusing on crypto assets. The mention of sell/spend/exchange as disposals further pins down the domain.

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 description implies when to use it (for calculating Japanese crypto tax) but offers no explicit when-not-to-use guidance or alternatives. It does not contrast with other jp_* tools, so an agent must infer its scope. While the purpose is clear, the lack of explicit routing leaves some ambiguity.

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