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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description's main added content is the return-value shape, but an output schema already exists, so that information is largely duplicative; the French alias is the only genuinely additive context.

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?

Three short, front-loaded sentences with the purpose stated first. The 'Returns: {...}' clause is redundant given the output schema and slightly dilutes an otherwise tight description.

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 read-only calculator with full schema coverage, complete annotations, and an output schema, the description covers the essential purpose and offers a cross-reference to related calculators. It is sufficient to call the tool correctly, though it lacks sibling routing.

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%, with loan_amount, duration_years, and rate_pct (including the 0.36 default) all documented in the schema. The description adds nothing about parameter formats or units, 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 verb and resource ('Calculate mortgage insurance cost') and clarifies the domain term with the French synonym 'assurance emprunteur', which helps disambiguate for a multilingual catalog. It does not distinguish itself from near-neighbors such as calculate_insurance_estimate, calculate_mortgage, or calculate_travel_insurance, so it stops short of 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?

There is no explicit when-to-use or when-not-to-use guidance. The only pointer is 'See list_bundles for related immobilier calculators', which is a browse hint rather than a routing rule telling the agent when this tool beats calculate_insurance_estimate or calculate_mortgage.

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