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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds the per-call cost of 1 credit and defines the output as the final amount A, but it does not discuss return formatting, precision, or behavioral edge cases. Given the annotation coverage, a 3 is appropriate.

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 front-loaded sentence that states the operation, formula, variable definitions, and cost. Every clause contributes to understanding how to use the tool, with no redundant or filler content.

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 simple read-only calculator with rich schema descriptions and no output schema, the description supplies the formula, variable meanings, final-amount definition, and cost. Combined with the annotations and schema, an agent has enough information to 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?

Schema description coverage is 100%, and the schema already documents each parameter’s type, units, and required status. The description largely maps formula symbols back to those parameters without adding new constraints or edge-case behavior. The formula relationship is useful context, but the schema still carries most of the parameter meaning.

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 verb and resource: it calculates compound interest. Supplying the exact formula and defining each variable makes the calculation unambiguous. It does not explicitly distinguish this tool from sibling calculators such as calculate_interest or future_investment_value, so it falls short of a 5.

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 explains the calculation but gives no guidance on when to use this tool rather than the many sibling finance calculators. It names no alternatives and states no exclusions or selection criteria, leaving the agent to infer usage from the tool name alone.

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