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

No annotations exist, so the description carries the full burden. It does add genuinely useful behavioral context beyond the schema: the tool is a paid operation costing $0.005 USDC via x402. However, it omits anything about what happens on out-of-range dates, error behavior, or why it is read-only.

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 compact sentences that front-load the resource and its returned content, with the pricing appended as a distinct clause. No filler, though the pricing sentence could be slightly tighter.

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 single-parameter lookup with no output schema, the description usefully enumerates the returned fields (rokuyo, era date, lunisolar date, solar terms) and discloses the cost, which is what an agent most needs to call it correctly. Missing only guidance relative to the related lucky-day sibling.

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?

With a single parameter and 100% schema description coverage, the schema already documents the 'date' field and its valid year range (1955-2032). The description adds nothing additional about the date format or semantics, so the baseline of 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 a specific resource (Japanese traditional calendar for a date) and enumerates the exact outputs: rokuyo lucky days, Reiwa era date, lunisolar date, and 24 solar terms. This is far more informative than the sibling names alone, though it stops short of explicitly distinguishing itself from find_lucky_days_japan.

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?

No when-to-use or when-not-to-use guidance, and no mention of the very close sibling find_lucky_days_japan, which also deals with lucky days. The only contextual signal is the price, which hints at a paid lookup but gives no invocation guidance.

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