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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and the description goes beyond them by disclosing the computed outputs — ratio, equity, and the paydown required to reach 80%. With no output schema present, this is the only place the return content is described, so it adds real value; it stays short of explaining how the currency parameter affects results.

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 example is front-loaded and immediately conveys the calculation, followed by a single invocation sentence, with no filler. The appended web-page URL is minor extra material but not enough to undermine the tight structure.

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 three-parameter calculator with full schema coverage and annotations covering safety, the description supplies purpose, required inputs, and the three output values — enough for an agent to call it correctly. The only omission is any note on currency handling, which is a modest gap given there is no output schema.

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 loan, value, and currency are already documented in the schema, establishing a baseline of 3. The description only restates balance and property value (and echoes the defaults in its example) without adding meaning such as how the currency enum affects output or whether it converts or merely labels.

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?

Names a specific computation (loan-to-value ratio) and illustrates it with a concrete worked example ($240,000 on a $300,000 home = 80% LTV), so the tool's purpose is unambiguous. It does not, however, distinguish itself from adjacent siblings like mortgage_calculator, heloc_calculator, or down_payment_calculator.

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?

"Enter your balance and property value to see your ratio, equity and the paydown needed to reach 80%" implies the use case (checking LTV and how to get under 80%) and tells the agent what inputs to supply. There is no explicit when-to-use/when-not guidance and no alternative sibling is named for disambiguation.

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