Compare regular vs direct plan drag

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

With no annotations provided, the description carries the disclosure burden, and it does so well by stating this is 'pure arithmetic on the numbers you supply'—communicating determinism, no data fetching, and no side effects. It also explicitly disclaims advice/recommendation behavior. It stops short of describing the exact return format, but the core behavioral traits an agent needs are clearly disclosed.

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 with no filler: the operational behavior is front-loaded and the disclaimer earns its place by preventing misuse. The em-dash extension adds context without bloating the description.

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?

The description is appropriate for a simple computational tool and covers what the tool computes and its scope. Yet with no output schema and no annotations, it leaves out explicit details such as the returned value, compounding convention, and parameter units, which would make invocation fully unambiguous.

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 description clarifies the roles of regularExpensePct and directExpensePct as the 'two expense ratios' and years as the 'holding period,' supplementing the sparse schema. However, with schema coverage only at 40%, it does not fully explain the formula relation of amount and assumedReturnPct or the units/output precision, leaving the agent to infer some parameter semantics.

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 identifies a specific operation—compounding the difference between two expense ratios over a holding period—and makes the output purpose explicit: showing what a fee difference costs. It also explicitly distinguishes itself from a recommendation tool ('does not recommend a fund'), which sets it apart in a sibling list dominated by data-lookup tools.

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 use when one wants to quantify the cost of an expense-ratio difference over time and explicitly warns it is not for fund recommendations. It does not name sibling alternatives or give explicit selection conditions, so the agent must infer suitability from the calculation phrasing rather than from a routing rule.

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