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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds the meaningful constraint that this only applies to fixed-rate loans, but it does not state payment timing assumptions (e.g. end-of-period monthly payments) or that the result ignores fees.

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?

A single sentence that leads with the returned values and ends with the required inputs, with zero filler. Every clause earns its place.

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?

There is no output schema, so the description correctly carries the burden of naming the three return values, which it does. It leaves out assumptions about rounding and payment timing, which are the remaining gaps for a financial calculator.

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 three parameters are fully documented in the schema, and the description only restates them in prose (amount, APR, term in months). No extra syntax or format guidance is added, so baseline 3 applies.

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 names the exact outputs (monthly repayment, total repaid, total interest) and the inputs (amount, APR, term in months), which makes the purpose concrete. It does not distinguish itself from sibling mortgage_calculator, so an agent has to infer that this is the generic consumer-loan version against the property-specific one.

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?

Usage is only implied by the phrase 'fixed-rate loan' and the presence of an APR-in-months-term input set. There is no explicit when-to-use, when-not-to-use, or routing to mortgage_calculator, which is the obvious alternative.

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