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

Annotations already declare a safe, idempotent read. The description adds genuinely useful behavioral context beyond them: it discloses that the notary fee is never computed ('no tariff') and that the agent commission has no legal rate. These caveats prevent wrong expectations about what the tool returns.

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 front-loaded 'ITALY. Computes...' opening is good, but the content is a single dense run-on sentence packing rates, minima, and conditions. Every clause carries real information, yet the absence of any sentence breaks or structure makes it hard to parse quickly.

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 7-parameter tax calculator with no output schema, the description covers the full computation logic and explicitly states what is excluded (notary fee). It is nearly complete, though it could note the currency of return values or the basis of the computed total.

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 coverage is 100%, which sets a baseline of 3, but the description goes further by tying parameters to outcomes (first_home → 2% registration/VAT relief, luxury_category A/1 A/8 A/9 → 22% and exclusion from relief, seller → private/builder, cadastral_income → prezzo-valore). This adds computational meaning the schema descriptions alone do not convey.

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?

Opens with 'ITALY. Computes the national purchase taxes', naming a specific verb and resource within a named jurisdiction. It clearly separates itself from siblings like purchase_costs_de/es/br and frais_notaire_fr by scoping to Italian national purchase taxes.

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 implicitly routes usage through scenarios: 'resale from a private owner' vs 'new build from a builder', and notes the mortgage substitute tax and agent commission are optional. It does not explicitly name an alternative sibling or state when NOT to use it, so it stops just short of full guidelines.

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