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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds behavioral context by illustrating how inputs transform into the true rate (the 7%/$1,000-fee example), but it says nothing about response format or what values are returned beyond 'rate, payment and full cost'.

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 tight sentences lead with the value proposition and an illustrative example, which is well front-loaded. The trailing URL is extraneous filler that a tool description does not need, slightly diluting an otherwise efficient blurb.

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 should hint at returns; it does mention the true rate, payment, and full cost of borrowing. With full schema coverage and annotations covering behavior, this is nearly complete, though it stops short of specifying the exact returned fields.

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 every parameter (fees, rate, term, amount, currency) is already documented with type, bounds, default, and description. The description's example maps loosely onto rate=7 and fees=1000 but adds no syntax or format detail beyond the schema. 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?

States a specific verb and resource: it folds origination fees and points into the true APR, payment, and total cost of borrowing. The concrete 7%/$1,000-fee → 9.17% example makes the purpose instantly clear. However, it does not differentiate itself from the many sibling loan calculators (loan_calculator, auto_loan_calculator, mortgage_calculator), so an agent has no routing cue.

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 provides no when-to-use or when-not guidance and never names an alternative sibling. A user wanting a plain monthly payment might reasonably pick loan_calculator instead; nothing here says when APR is the right metric. Usage is only implied by the example.

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