Amortization Schedule

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

The description adds substantial behavioral context beyond the readOnlyHint: it discloses the last-row zeroing correction, the monthly vs. daily compounding distinction, refusal behavior for negative amortization and unparseable dates, and a disclaimer field that must be relayed. This goes well beyond what annotations convey.

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 long but appropriately so for a 10-parameter tool. It front-loads the core purpose, then moves from usage scenarios to failure modes to parameter semantics to return value and disclaimer. Each section earns its place, and the numbered failure modes make the content easy to parse.

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?

With no output schema, the description carries the full burden of explaining return values, and it does: full schedule, total interest and PMI, payoff period, final payment delta, and comparative no-extra-principal schedule. Refusal conditions and edge cases are also covered, so an agent has enough context to invoke and interpret the tool correctly.

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?

Although schema coverage is 100%, the description adds essential semantic detail: which parameters are required, the mutually exclusive startDate/dayCountBasis condition, the distinction between oneOff and recurring extraPrincipal shapes, PMI cancelAtPercent defaults, and that biweekly requires daily compounding. This materially helps an agent construct valid calls.

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 opens with a specific verb and resource: 'Builds the full row-by-row amortization schedule for a loan — interest, principal, PMI, and running balance for every payment.' It clearly distinguishes the tool from merely computing a monthly payment amount, which removes ambiguity about scope.

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 gives explicit when-to-use guidance with concrete examples: balance after payment 47, extra principal effects, PMI drop-off timing, or the whole table. It also warns against doing the arithmetic manually and lays out conditional usage rules for daily compounding, startDate vs. dayCountBasis, and payment frequency.

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