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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is clear. The description adds meaningful behavioral context by disclosing the exact down payment tiers and that it also reports CMHC insurance applicability and premium rate, though it does not discuss output format or edge-case limitations.

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 a single front-loaded sentence that immediately states the main calculation, followed by necessary rule detail in a parenthetical. Every clause earns its place by specifying the calculation and outputs.

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 one-parameter calculator with no output schema, the description sufficiently explains what is computed and returned: the minimum down payment, whether CMHC insurance applies, and the premium rate. An agent has enough context to invoke it correctly.

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?

The single homePrice parameter has 100% schema description coverage, so the schema already defines its meaning and constraints. The description does not add parameter-level detail beyond what the schema provides, making the baseline score appropriate.

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 (Calculate) and resource (minimum down payment) with the exact Canadian CMHC rule set and additional outputs (CMHC insurance applicability and premium rate). The scope is unambiguous and clearly distinct from sibling mortgage or tax calculators.

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 implies when the tool is useful by stating its purpose, but it does not explicitly say when to use it versus alternatives such as mortgage_payment or mortgage_affordability. No exclusions or routing guidance are provided.

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