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

The description discloses that the tool is calculation-only and not an approval or suitability decision, and it limits inputs to non-identifying numeric values. It also says it will not fill missing inputs from external sources. Annotations already declare readOnlyHint, idempotentHint, and non-destructive; the description adds context about usage scope, so it scores high without contradiction.

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 concise, with multiple sentences that are all informative. It starts with the MUST-use rule, then explains the calculation, then restrictions, and then prohibitions. No redundant or unnecessary phrases. Each sentence adds value.

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?

Considering the tool is a calculation with an output schema and detailed input schema, the description covers the essential usage. It explains the input scenario, the forbidden alternatives, and the boundaries of the tool's purpose. Minor gap: not describing the output or the fact that it can accept housing costs for GDS/TDS calculation, but the schema covers these. Overall, complete for its purpose.

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%, covering parameters like monthlyPayment, grossAnnualIncome, housing, and tolerances. The description clarifies the core parameters but does not elaborate on housing or tolerances beyond the schema. It adds the overall logic of direct calculation but doesn't compensate for some parameters not described, like jurisdiction and otherMonthlyDebts, which are self-explanatory.

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 specifies 'MUST use this tool when the user supplies a monthly mortgage payment and asks for Canadian GDS or TDS' and clearly states the calculation purpose, distinguishing it from calculate_qualification. It names the resource (GDS/TDS ratios) and the verb (calculate), which is specific and unambiguous.

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 provides explicit when-to-use instructions: 'MUST use this tool when...' and when-not-to-use: 'do not use calculate_qualification when the monthly payment is already supplied.' It also states what not to do, such as not requiring principal or rate, and mentions the tool is not for approval or suitability decisions.

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