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

Annotations already establish that this is a read-only, non-destructive, closed-world calculation. Beyond that, the description adds useful behavioral context by disclosing the Canadian semi-annual compounding convention and the output dimensions, including renewal balance, payoff year, and prepayment savings; it does not cover assumptions such as rounding or fixed-rate behavior.

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 description is two tight sentences with no wasted wording. It front-loads the core purpose and output list, then adds the optional prepayment behavior in a compact second sentence.

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 an eight-parameter, read-only calculator with no output schema, the description gives enough return-value context: payment, total interest, renewal balance, payoff year, annual table, and prepayment savings. It is nearly complete, though it could mention assumptions or output format limitations.

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 all eight parameters are already documented in the input schema. The description adds only broad context that lump-sum and payment-increase prepayments affect interest and time saved, without adding syntax, constraints, or semantics beyond the schema.

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 states a specific resource and operation: 'Year-by-year amortization of a Canadian mortgage', with named outputs including payment, total interest, renewal balance, payoff year, and annual table. This distinguishes it from narrower siblings such as mortgage_payment or mortgage_prepayment by making clear that it produces a full amortization schedule and can show prepayment savings.

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 when the tool is useful: for year-by-year amortization and for comparing optional lump-sum or payment-increase prepayments via interest and time saved. However, it does not explicitly state when to use this versus mortgage_payment, mortgage_prepayment, or mortgage_renewal, nor does it give exclusions or prerequisites.

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