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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds domain behavior (semi-annual compounding per Canadian law, CMHC premium inclusion, accelerated payment options) but says nothing about the output format or how premiums are surfaced in results.

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 tight sentences with the capabilities front-loaded, followed by a reference URL that is arguably useful rather than padding. No wasted words, though the URL is tangential to tool invocation.

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 no output schema, the description should indicate what the calculator returns (e.g. payment amount, CMHC premium, total interest), but it only lists features. The input side is complete via the schema; the output side is left unspecified.

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%, so the schema already documents all six parameters including the semi-annual compounding note on rate and the first-time-buyer rule on buyer. The description's feature list mirrors that content without adding syntax or meaning beyond the schema, so the baseline 3 applies.

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 resource (Canadian mortgage payments) and lists distinguishing features: semi-annual compounding, CMHC premiums, minimum down payment, accelerated bi-weekly/weekly. This implicitly separates it from the generic mortgage_calculator and dubai_mortgage_calculator, but it never names or contrasts those siblings explicitly.

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 word 'Canadian' implies the domain, but there is no explicit when-to-use or when-not-to-use guidance, no mention of alternatives like mortgage_calculator or down_payment_calculator, and no prerequisites. The agent must infer routing from the name alone.

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