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

Annotations already declare a pure computation (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the safety profile is covered. Beyond that the description adds real behavioral context the annotations cannot: the result includes reasons, GDS/TDS is computed separately in each category at that category's rate, and renewals hinge on whether a premium was paid at origination — a non-obvious business rule. With no output schema, it also sketches the return shape.

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 sentences, front-loaded with the classification output, then the renewal dependency last. No filler or restatement of the title. It is dense but every clause carries information; only the parenthetical purpose list borders on enumerating schema content.

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 18-parameter, no-output-schema tool the description covers what comes out and one key rule, but the underlying classification criteria (loan-to-value thresholds, amortization limits, unit/occupancy effects) are never hinted at, so an agent cannot predict which inputs drive the verdict. The illustrative-default warning lives only in the schema. Adequate but leaves meaningful gaps for a tool of this complexity.

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% across 18 parameters, so the schema already documents units, occupancy, purpose, rates, and amortization. The description only adds meaning for one parameter class, linking premiumPaid to the renewal rule in the final sentence. That is a marginal gain over a fully documented schema, which is the baseline-3 case.

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 names a specific verb and output ('classifies a mortgage as insured, insurable or uninsurable') plus the transaction types covered (purchase, renewal, switch, refinance) and a secondary function (GDS/TDS per category at its rate). An agent can tell this apart from generic siblings like debt_service_ratio or mortgage_qualifier because it produces a three-way classification plus per-category ratios. It stops short of explicitly naming the sibling it replaces, so not 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?

The 'Broker tool' framing and the list of covered purposes imply when it applies, and the closing sentence signals that renewal cases need premiumPaid. However, there is no explicit when-to-use versus mortgage_qualifier, cmhc_insurance, or debt_service_ratio, and no statement of when this tool is inappropriate. Usage is inferable but left to the agent.

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