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

Annotations cover safety (idempotent, non-destructive), but the description adds valuable context beyond them: pricing ($0.02/call), determinism, primary-source citation, and a billing policy (errors and unverified rules are never billed). The x_payment parameter and its no-charge path reinforce the payment model. Return format is left to the output schema, which is acceptable.

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?

Two dense sentences, front-loaded with the core purpose, followed by pricing and guarantees. Every clause carries information; no filler. Could be marginally tighter but is well-structured and appropriately sized.

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 full output schema present, return values needn't be described, and the schema plus 100% coverage handles parameters. The description supplies the behavioral context an agent needs (determinism, pricing, billing policy). The main gap is the absence of sibling routing guidance, which the crowded namespace makes notable.

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 documents all six parameters including the nested payslip object and the x_payment header. The description does not add any parameter-level meaning (no format, defaults, or interaction details beyond the schema), so the baseline 3 is correct.

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 (audit) and resource (Japanese payslip) and details the operation: recompute statutory premiums and withholding tax from official tables and diff against actual amounts. The per-item verdict taxonomy (match/explainable/mismatch) further distinguishes it from siblings like jp_payroll_net or jp_social_insurance, which compute rather than audit.

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 usage (auditing an existing payslip against statutory tables) but never states when to pick this over the crowded sibling set (jp_payroll_net, jp_social_insurance, jp_payroll_suite). It offers no explicit alternatives or when-not conditions, leaving routing to inference.

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