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

Annotations already declare idempotent=true, destructive=false and openWorld=true, so safety is partly covered. The description still adds real behavioral value beyond the schema: per-call pricing ($0.02), determinism, primary-source citation, and a no-charge-on-error policy, plus the x_payment parameter documents a dry-run payment-requirements flow.

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?

Three tight, front-loaded fragments with no filler; the core computation leads and pricing/behavioral caveats follow. Every sentence earns its place, though the terse fragment style slightly reduces readability.

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?

With a 100%-covered schema and an output schema present, return values need no explanation and the description wisely omits them. It covers rules and billing behavior adequately; the only notable gap is routing guidance relative to sibling tax tools.

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 description coverage is 100%, so the schema already explains all five parameters including the payment header, disability and officer flags. The description references years-of-service deduction logic but adds no syntax, format, or edge-case detail beyond that, so the baseline 3 applies.

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 the resource precisely (retirement income tax) and the specific computation enclosed (deduction by years of service, half-taxation rules, withholding rounding), so an agent knows exactly what output to expect. It does not, however, differentiate itself from the dense cluster of jp_* payroll/tax siblings (e.g. jp_payroll_net, jp_consumption_tax), leaving the agent to infer the boundary.

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, no prerequisites, and no named alternative among the many sibling tools that also compute Japanese income taxes. The agent must guess whether this is the right tool versus jp_payroll_net or jp_payslip_audit.

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