validate_invoice_on_date

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

With no annotations provided, the description carries the full burden. It discloses that the operation is a confirmation (read-only in nature) and specifies the return format (markdown). However, it does not mention any prerequisites, error conditions, or potential side effects. For a simple validation tool, this is adequate but not comprehensive.

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 concise and well-structured. The main purpose is stated in the first sentence, followed by a clarifying sentence, then a clear Args/Returns section. There is no unnecessary verbosity; every sentence adds value.

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?

The tool is simple with two parameters, and the description covers them well. However, it does not provide an output schema, and the return description is vague ('指定日時点の登録状態（マークダウン）'), leaving the exact structure of the markdown unspecified. For an agent to fully understand the response, more detail would be helpful, but it may be sufficient for a simple status check.

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?

The schema provides no descriptions (0% coverage), so the description must fully explain parameters. It does so excellently: 'number' is described as a registration number with format (T+13 digits) and an example; 'day' is described as a date with format (YYYY-MM-DD) and an example. This adds essential meaning beyond the schema.

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 tool's purpose: checking invoice registration validity as of a specific date. It uses a specific verb (確認する) and resource (登録有効性), and includes an additional explanatory sentence. However, it does not explicitly differentiate from the sibling 'check_invoice_registration', though the date-specific aspect is implied.

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 implies usage for checking historical registration status ('特定の取引日に'), but it does not explicitly state when to use this tool over alternatives, nor does it mention any exclusions. It would benefit from referencing the sibling tool for current-status checks.

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