calc_mortgage

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered by structured data. The description adds nothing beyond restating the purpose – it doesn't mention the amortization assumption (fixed-rate, equal payments), rounding, or that the result is a single monthly figure. With annotations carrying the safety burden, a 3 is the ceiling here.

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 clean sentence with no waste, but it is under-specified rather than concise. The brevity comes at the cost of the parameter and output information an agent needs.

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 3-parameter financial calculator with no output schema and no parameter descriptions, the definition is too thin. The agent cannot know the rate format, the return shape (payment amount only? total interest?), or the repayment model, all of which materially affect whether the call is correct.

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 0%, so the description must compensate and it does not. Critical ambiguities remain: is annual_rate a percentage (5.5) or a decimal fraction (0.055)? Is principal in dollars or cents? Can years be fractional? None of this is addressed.

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 ('Calculate monthly mortgage repayment'), which is unambiguous. It does not differentiate against related siblings such as calc_compound_interest or calc_tip, which share the same numeric-calculator space, so it stops short of a 5.

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?

No guidance on when to use this versus calc_compound_interest or calc_currency_estimate, and no prerequisites mentioned. The agent must infer the use case entirely from the name.

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