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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered without the description. The description adds computational context (it enumerates what gets modelled), but it does not disclose assumptions such as how standby months interact with the amortization clock, or that the tool is a pure calculation with no persistence. Much of the "Returns ..." sentence duplicates the output schema.

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?

Three well-ordered sentences: what it models, what it returns, when to call it. Purpose is front-loaded and there is no filler. The output enumeration is dense and partly redundant with the output schema, which keeps 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 10-parameter pure calculator with a full output schema and complete annotation coverage, the agent has enough to call it correctly: purpose, mode options, and trigger are all stated. What is missing is sibling disambiguation and any note on the interplay between maturityYears and amortizationYears beyond the schema's one-line hint.

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 coverage is 100%, so the baseline is 3 and the schema already explains units, defaults, ranges and both enums in detail. The description adds only framing for the parameter families (repayment mode, standby treatment, coverage inputs), which is marginal but not zero value.

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?

Opens with a specific verb and resource: "Model seller financing in a business acquisition," and names the mechanics it covers (amortizing or interest-only, standby months, interest treatment). It is clear on its own, but it never distinguishes itself from the sibling model_acquisition_loan, which an agent could plausibly reach for on the same request.

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?

"Use when the user asks what a seller note costs or what is owed at the end" gives an explicit trigger in user-intent terms, which is genuinely useful for routing. There are no exclusions or named alternatives, so the agent must infer that senior/debt financing belongs to model_acquisition_loan or build_capital_stack.

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