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

Annotations already declare the tool as read-only and idempotent. The description adds context about the computational approach (comparing gross vs net balances and the fee loss), which is valuable. No contradiction exists, and the description does not omit any major safety or behavioral caveats.

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, well-structured sentence that leads with the core purpose ('Effect of an annual fee') and efficiently explains the outputs. Every word contributes meaning; there is no redundancy or filler.

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?

Given the tool's simplicity, a fully documented schema, and the presence of an output schema, the description is sufficiently complete. It conveys the essential outcome without needing to elaborate on return formats or assumptions.

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 provides 100% coverage with clear descriptions for all four parameters (principal, grossAnnualPct, feePct, years). The description does not add parameter-specific details beyond what the schema already contains, so it does not exceed the baseline for high schema coverage.

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: it calculates the effect of an annual fee on a compounded balance, comparing gross vs net growth and quantifying the amount lost to fees. This specific verb-resource combination distinguishes it from siblings like compound-interest or cagr.

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 (when you want to see the impact of annual fees on investment growth) but does not explicitly state when to use this tool over alternatives or provide exclusion criteria. Sibling tools like compound-interest are not mentioned, so the guidance is only implicit.

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