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

With no annotations, the description carries the full burden of behavioral disclosure. It discloses a key trait: the cost ($0.01 USDC via x402), which is valuable. However, it does not mention error handling, rate limits, authentication requirements, or whether the operation is read-only (though calculation implies no side effects). It adds some context (settlement/delivery) but lacks deeper behavioral detail.

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?

The description is a single sentence that front-loads the core action and purpose, then adds a concise price note. Every word earns its place; there is no filler or redundant repetition of the schema.

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 3-parameter tool with no output schema, the description covers the essential use case and cost. It does not explicitly state the return format (likely a date), but that is implied by the operation. The schema already documents parameter ranges and the calendar enum. The description is sufficient for an agent to call it correctly, though a note on return format would be a minor enhancement.

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 67% (date and calendar have descriptions, but days does not). The description compensates by explaining that 'days' is the number of Japanese business days to add or subtract, clarifying the semantic of the days parameter. It also reinforces the operation's purpose, adding value beyond the schema's enum/type definitions.

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 the action ('Add or subtract N Japanese business days from a date') with a specific resource (business days, Japanese) and concrete use cases (settlement T+N, delivery ETA). This distinguishes it from siblings like is_business_day (a boolean check) and list_holidays (listing holidays). The verb-resource pair is specific and unambiguous.

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 provides clear context for when to use this tool (settlement/delivery date calculations) by naming the exact business scenarios. However, it does not explicitly mention alternatives or exclusions (e.g., 'for checking if a date is a business day, use is_business_day'). The guidance is strong but not fully explicit about when not to use it.

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