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 useful traits: the holiday-adjustment rule for the SQ date and that invocation costs $0.01 USDC via x402. However, it omits the return format, behavior for invalid months, and any error semantics.

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-loading the core function followed by the pricing note, with no wasted words. It could be slightly tighter but every sentence carries signal.

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 deterministic date calculation with no output schema, the description adequately explains what is computed and the governing rule. The absence of a stated output format is a minor gap given the tool's low complexity.

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 coverage is 100% and the single 'month' parameter is fully documented as YYYY-MM in the schema. The description's phrase 'for a contract month' reinforces the intent but adds no format or constraint detail beyond the schema, so 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 computed resource (Nikkei 225 futures/options SQ day and last trading day) for an input contract month, and even encodes the underlying rule (2nd Friday, holiday-adjusted). This clearly distinguishes it from generic date siblings like is_business_day, though it never explicitly positions itself against the close siblings jpx_record_date and jpx_trading_day.

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 and no mention of the alternatives (jpx_record_date, jpx_trading_day) or when each is appropriate. The only context offered is the price, which is a cost note rather than a selection cue.

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