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

Annotations already cover readOnly, idempotent, closed-world, non-destructive, so the bar is lower; the description still adds real context by clarifying that the output is ratios only and not an approval or suitability decision. It also discloses that no values are retrieved from chats, files, accounts, documents, or the web, going beyond the openWorldHint alone. Return shape is not described, but an output schema exists.

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?

Front-loaded with the calculation and its input contract, which is the right ordering. The disclaimer about approval/underwriting/suitability is stated twice ('not an approval or suitability decision' and 'no approval, underwriting, or suitability decisions'), which is avoidable repetition.

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 rich annotations and a machine-readable output schema, the description need not explain return values, and it covers the key input contract and scope limits. Minor gaps remain around tolerances, effectiveDate semantics, and jurisdiction that only the schema handles.

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 71% (high), so the schema already documents payment, income, housing costs, and debts. The description adds meaningful framing on monthlyPayment (taken as given, no derivation needed), but says nothing about effectiveDate, tolerances, or jurisdiction beyond the schema's own descriptions.

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 (calculates) and precise resource (Canadian GDS and TDS ratios) and immediately scopes the input shape: a monthly payment that is already known, not derived. This cleanly separates it from siblings like calculate_ltv and calculate_qualification, which operate on different inputs.

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?

Explicitly states the prerequisite that the payment is given and that no principal, rate, or amortization is needed, which tells the agent when this tool applies versus a payment-derivation tool. It also constrains inputs to explicit non-identifying numbers, but never names a sibling by name as the alternative.

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