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

Annotations already cover readOnlyHint and openWorldHint, yet the description adds meaningful context beyond them: check-digit rejection of malformed numbers with no upstream call, the fact that results are not stored, and the per-call price/payment rail. It stops short of describing latency, rate limits, or error responses, but this is a substantive addition.

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?

Three tight sentences, front-loaded with the core purpose and followed by the validation and pricing caveats; no filler. The pricing sentence is operationally relevant for an x402-paid tool rather than waste.

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 tool with no output schema, the description names the returned semantics (status plus VAT taxpayer type) and discloses validation and billing behavior, which is close to complete. It could go further by noting the response shape or failure modes, but nothing critical is missing.

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 b_no parameter is already fully documented as a 10-digit number, so the schema does the heavy lifting. The description reinforces the format constraint via the check-digit rejection note but adds no syntax or formatting detail beyond it — 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?

States a specific verb+resource (check a Korean business registration number) and enumerates the exact outputs: active/suspended/closed status and VAT taxpayer type. It does not, however, differentiate from the sibling kr_business_status_batch, which an agent selecting between single and batch modes would need.

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 KYB framing implies the use case (verifying a company before onboarding/transacting), but there is no explicit when-to-use versus when-not guidance and no mention of the batch sibling as the alternative for multiple numbers. Usage is inferable rather than stated.

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