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

Annotations already cover read-only, idempotent, closed-world, non-destructive, so the bar is lower. The description still adds substantive domain behavior: the 2026 reference year, the concrete sector thresholds (143 / 186 points), the fact that increase caps are sector-dependent, and the upstream data source. It omits how proposed_increase_pct is evaluated and what happens when current_rent is absent.

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?

A single front-loaded sentence that leads with the applicable scope before the computation, with the exclusion clause placed at the end where it belongs. It is dense with parentheticals (Dutch terms, thresholds) but every clause carries information; no filler.

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?

There is no output schema, and the description compensates by enumerating the return values (sector, legal max basic rent, above-max flag, max yearly increase). Combined with annotations and full schema coverage this is close to complete; only the treatment of the optional proposed_increase_pct and missing current_rent remains 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 baseline is 3. The description reinforces that points come from the Huurprijscheck and that rent means kale huur without service costs, and it explains the threshold logic that gives the points parameter meaning, but it does not add syntax or format detail beyond the schema.

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?

Names a specific computation (legal maximum rent and allowed increase) on a specific resource (Dutch rent points / WWS for an independent home), and enumerates the concrete outputs: sector, legal max basic rent 2026, whether current rent exceeds it, max yearly increase. Nothing in the sibling set (car_by_plate, monthly_budget_by_city, nl_current_facts) overlaps, so an agent can route unambiguously.

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?

Gives clear applicability scope: rented independent home with own front door, kitchen and toilet, and explicitly excludes rooms (onzelfstandige woonruimte) which use a different table. It also tells the agent where the points input must come from (Huurprijscheck on huurcommissie.nl). It does not name a competing tool or state a triggering user intent, so it falls short of a 5.

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