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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral context by disclosing that it returns both the rule-of-72 estimate and the exact compound-formula doubling time, which is important since no output schema exists.

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 two tightly written sentences with no filler. The primary purpose is front-loaded, followed immediately by the required rate constraint.

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 one-parameter calculator with annotations and no output schema, the description is nearly complete: it states what is computed, what is returned, and the valid input range. It could be slightly more explicit about units (e.g., years), but the missing detail is minor.

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%, so the single rate parameter is fully documented in the schema. The description restates the 0–30 percent range and frames it as an annual growth rate but adds no format or syntax beyond the schema, making the baseline score of 3 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 uses a specific verb and resource: 'Estimate the doubling time of money at a fixed rate using the rule of 72, plus the exact doubling time from the compound formula.' It clearly distinguishes itself from broader finance siblings like compound_interest by naming the rule-of-72 method and stating the exact dual output.

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 gives a concrete usage constraint — 'Rate must be between 0 and 30 percent' — which is a prerequisite for correct invocation. However, it does not explicitly say when to prefer this tool over alternatives such as compound_interest or cagr, leaving comparison to inference.

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