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

Annotations already declare readOnlyHint=true and idempotentHint=true. The description adds the exact formula and output unit ('in percent'), which is valuable behavioral context beyond the annotations. It does not contradict annotations.

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 sentence with a compact formula. No wasted words, information is front-loaded, and it is immediately actionable.

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?

With an output schema and 100% parameter coverage, the description is mostly sufficient. However, the formula references 'capital gain' without explicitly stating it equals endValue - beginValue, leaving a minor ambiguity in how inputs map to the calculation. Also, no mention of edge cases (e.g., zero starting value) is made.

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 coverage is 100% with descriptions for all three parameters ('Income received over the period.', 'Ending value.', 'Starting value.'). The description adds no extra semantic detail to the parameters; it only restates the formula, so baseline 3 is 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 defines the tool as computing holding-period return with an explicit formula: '(income + capital gain) / starting value, in percent.' The resource (holding-period return) and calculation scope are specific, and the formula distinguishes it from sibling metrics like CAGR or ROI.

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 usage via the formula (e.g., when income and beginning/ending values are known) but provides no explicit context, exclusions, or comparisons to alternatives like 'cagr' or 'roi'. No direct guidance is given.

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