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

No annotations are provided, so the description carries the full burden. It discloses that the tool is 'Browser-based' and 'instantly' reverse-calculates, but it does not detail the calculation assumptions, required user inputs, or expected interaction flow. This is adequate for a simple calculator 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 a single concise sentence with a parenthetical note, front-loading the core function with no wasted words. It efficiently communicates the purpose and platform.

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 zero-parameter browser tool, the description is sufficiently complete: it names the output (deduction upper limit) and the platform. It doesn't describe an interaction flow, but the simplicity of the tool and the empty schema make that less critical.

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 input schema has zero parameters, so there are no parameter semantics to clarify. The baseline of 4 applies, and the description adds no parameter information because none exist. This 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 states a specific action: 'reverse-calculates the deduction upper limit that keeps self-payment at 2,000 yen.' This clearly identifies the tool's function and differentiates it from sibling tax calculators like resident-tax-calc or tax-return-calc by focusing on the unique furusato tax threshold.

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 the use case (calculating furusato tax deduction upper limit) but does not explicitly state when to use it over alternatives or mention any exclusions. The context is clear enough for an agent to infer, but it lacks direct comparative guidance.

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