calculate_extra_payment_impact

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds behavioral context by explaining that it returns a baseline vs. with-extra comparison and the specific metrics (months saved, interest saved), which is valuable beyond annotations. No contradictions.

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?

Two sentences, front-loaded with the core action, then output specifics, then a usage example. Every sentence earns its place with no redundancy or fluff.

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?

Even though there is no output schema, the description explains exactly what the tool returns (baseline vs. with-extra, months saved, interest saved) and when to use it. Combined with well-schema'd parameters and annotations, it is complete for a calculation tool.

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?

Input schema coverage is 100%, with each parameter described (debts, strategy, extra_monthly_payment_usd). The description itself doesn't add parameter-level detail, so the baseline of 3 is appropriate. The schema already does the heavy lifting.

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: showing the impact of extra monthly payments on debt payoff. It specifies the comparison (baseline vs. with-extra) and the key outputs (months saved, interest saved), which distinguishes it from sibling tools like calculate_debt_payoff.

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 explicitly identifies the trigger scenario: 'Use this when a user asks what happens if I pay $50/$100/$500 more per month?' This gives clear when-to-use guidance. It does not mention when not to use it or name alternatives, but the context is unambiguous enough.

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