Check a Japanese invoice registration number (T + 13 digits)

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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds real value beyond them: what normalization is applied, that only corporate check digits are correct, exactly which fields come back, and the important limitation that registration status is not verified.

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?

A single dense sentence covering normalization, validation, and return fields, followed by the offline caveat. Every clause earns its place and nothing is buried.

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?

There is no output schema, yet the description enumerates the returned fields, so an agent knows what to expect. Only the meaning of 'messages' and failure behavior are left unstated, a minor gap for a single-parameter validator.

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 0% for the single 'number' parameter, so the description must carry it, and it does: accepted input may be full-width, spaced, or hyphenated, and must normalize to 'T' + 13 digits. It stops short of giving an example value or describing the error/message content.

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 pair (normalize, check) and a precise resource: 'T' + 13 digits plus the corporate check digit. It is clearly narrower than siblings jp_invoice_check and jp_invoice_tax, but it never names or contrasts them explicitly.

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?

Usage is implied by the scope statement and the closing caveat 'Offline: registration status is not checked', which hints at when to reach for something else. However, no sibling is named and there is no explicit when-to-use/when-not-to-use routing.

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