必要月額逆算

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

No annotations are provided, so the description bears full responsibility. It conveys that the tool performs a calculation (read-only, non-destructive) and mentions that current savings are invested with compounding. It does not disclose any other behavioral traits (e.g., exact formula, assumptions, or response format), which is adequate for a straightforward calculator.

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 consists of two concise sentences in Japanese. The first sentence states the function and inputs/output, and the second gives a concrete usage question. There is no wasted text, and it is front-loaded with essential information.

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 calculator with four numeric parameters and no output schema, the description is sufficiently complete. It explains the input-output relationship clearly. It could be improved by noting assumptions (e.g., compounding frequency), but it is adequate for an agent to understand and invoke the tool correctly.

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?

All parameters are described in the schema with high coverage (100%). The tool description adds value by clarifying the overall purpose and providing context for the parameters (e.g., 'reverse calculation' and that current savings are compounded). This reinforces 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 function: reverse-calculate monthly contributions needed to reach a financial goal, given target amount, current savings, annual rate, and duration. It includes an example question, making the purpose unambiguous. This distinguishes it from siblings like calculate_compound_interest (forward calculation) and plan_retirement (broader planning).

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 frames the tool as answering 'how much to save monthly to reach X in N years', which implicitly guides when to use it. However, it does not explicitly state when not to use it or contrast it with siblings. The context from sibling names suggests alternatives, but the description itself lacks direct usage guidance.

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