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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the description's job is to add behavior — and it does, disclosing the DSCR is only returned when cash flow is supplied and that a balloon appears at maturity. It does not mention rounding, rate convention, or error behavior, which keeps it short of a 5.

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, front-loaded with the operation before the usage trigger; no filler. The enumeration of return values is mildly redundant given an output schema exists, which is the only thing keeping it from a 5.

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 single-purpose financial calculator with full schema coverage and an output schema, nothing an agent needs to call it correctly is missing — inputs, outputs, conditional DSCR behavior, and the usage trigger are all present.

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 already has units and defaults documented. The description restates the parameter list (principal, rate, term, amortization period, optional cash flow) and echoes the balloon/term relationship already in the amortizationYears schema text, adding no new semantics.

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 — 'compute the payment and amortization of a senior acquisition loan' — and enumerates the exact inputs and outputs. The 'senior acquisition loan' scope is clearly distinguishable from siblings such as model_seller_note or screen_sba_eligibility without opening any schema.

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?

Gives an explicit trigger: 'Use when the user asks what a loan of a given size costs each month or year.' That is a clear usage context, but no exclusions or named alternatives (e.g. when to prefer build_capital_stack or model_seller_note instead) are provided.

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