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

With no annotations, the description carries the full behavioral burden. It does disclose a key trait: paid access at $0.01 USDC via x402, which an agent needs before calling. But it omits return format, error behavior on dates beyond the 366-day cap, and payment failure handling.

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?

A single dense sentence that front-loads the core action and filters and appends the price last. Every clause (rokuyo, weekday options, use cases, cost) carries information; no filler.

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 4-parameter, no-output-schema tool, the description covers purpose, both filter dimensions, intended use cases, and pricing. The main residual gap is what the result looks like (list of dates vs. structured objects) and timezone/range semantics, which an agent must infer.

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 all four parameters are already documented in the schema, including valid rokuyo values and the date format. The description only echoes examples (taian, sat,sun), adding little beyond the structured fields, 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?

Specific verb (find) plus a precise resource (auspicious Japanese dates matching rokuyo and optional weekdays), with the domain concept (rokuyo/taian) named explicitly. An agent can distinguish this from generic business-day siblings like is_business_day or add_business_days.

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?

Use cases (weddings, moving, contracts) imply when the tool is relevant, and it names the two filtering dimensions. However, it never states when NOT to use it or points to the closest alternative (japanese_koyomi), which likely overlaps on rokuyo data, leaving the choice to inference.

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