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

With no annotations, the description carries the behavioral burden and does disclose meaningful traits: T+2 settlement logic, holiday-awareness, and a concrete cost of $0.01 USDC via x402 (payment requirement). It does not explain the return shape or whether the dates are returned as a pair, but the pricing and calendar-convention disclosures are real value beyond 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?

Two short sentences, front-loaded with the core computation and followed by the settlement caveat and price. No filler; each clause earns its place.

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 one-parameter calculation with no output schema or annotations, the description covers the domain meaning, the settlement convention, holiday-awareness, and the payment model. It could state what exactly is returned (the two dates, and their format) to be fully self-contained, but nothing critical 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 description coverage is 100% for the single recordDate parameter, and the schema itself glosses it as 'record date (kenri kakutei-bi) YYYY-MM-DD'. The description adds the semantic that it is a dividend/benefit record date, which is marginal beyond the schema, 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?

The description names a specific verb-like computation (last cum-rights trading day / ex-rights date) on a specific resource (Japanese stock dividend record date), which clearly separates it from siblings like jpx_sq_date or jpx_trading_day. It stops short of explicitly naming an alternative sibling, so it is clear but not maximally differentiated.

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?

Usage is implied by the finance domain (given a record date, derive the settlement-relevant trading dates) and the T+2 settlement note hints at context, but there is no explicit when-to-use statement, no prerequisite, and no comparison against the other date tools in the sibling list.

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