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

With no annotations, the description carries the full behavioral burden. It discloses the data source, return elements (holiday name in JA/EN and next/previous business day), and the price ($0.005 USDC via x402). For a read-only check, this is solid context. It does not mention rate limits or side effects, but none are apparent.

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 efficient sentences: the first states the purpose and data source, the second covers return value and price. No filler, all information is relevant, and the core action is front-loaded.

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 simple 2-parameter tool with no annotations and no output schema, the description covers the essentials: purpose, data source, return content, and cost. It does not detail the response shape or error handling, but the schema covers input constraints. It is complete enough for an agent to invoke correctly.

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 fully documents the 'date' format/range and 'calendar' enum/default. The description adds no extra parameter semantics beyond implying the date is what gets checked. It does not clarify edge cases or how the calendar parameter affects the return. Baseline 3 is appropriate.

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 clearly states a specific verb ('Check') and resource ('whether a date is a business day in Japan') and names the data source ('official Cabinet Office holiday data'). It also mentions the return content, which distinguishes it from siblings like list_holidays or add_business_days. The agent can tell what this tool does without opening the schema.

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 gives the context ('check whether a date is a business day in Japan') but does not explicitly discuss when to use this tool versus alternatives like is_business_day_free or add_business_days. It does not mention exclusions or trade-offs (e.g., the paid tier vs free version). Usage is implied rather than directly guided.

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