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

Annotations only declare read-only/idempotent/open-world; the description goes well beyond them by disclosing the exact price (0.04 USDC via x402 or 20 credits of a Factline API key), the free quota (first 5 paid-tool calls a day, no payment or key needed), and the upstream data sources (Kadaster, CBS, Politie, RIVM, RVO). For a paid tool, cost and auth are the highest-value behavioral facts an agent needs before invoking.

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?

It is a single dense paragraph with the trigger front-loaded and zero filler sentences; every clause (content list, inputs, sources, price) earns its place. It would scan better if split into trigger / contents / cost lines, which is the only reason it is not a 5.

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 substitutes by enumerating the report sections returned, and it covers inputs, sources, and payment paths. Given five mostly-optional parameters and non-trivial billing, an agent has everything it needs to decide and call 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?

Schema coverage is 100%, so the baseline is 3. The description only restates the primary input combination ("postcode + house number") and never mentions the free-text 'q' alternative, the optional addition/house_letter fields, or the zero-required-parameters property, so it adds little 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?

The description opens with a specific trigger ("Use when the user asks about a specific Dutch home or address before renting, buying or moving") and then enumerates exactly what the report contains, which makes it distinguishable from narrower siblings such as nl_home_basic, nl_crime, nl_energy_label or nl_neighbourhood: this is the aggregate report. Both the action and its scope are unambiguous.

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 "use when... before renting, buying or moving" framing gives a clear situational trigger and the input requirement (postcode + house number) tells the agent what it needs before calling. It does not name any alternative or exclusion, however, and with siblings like buy_full_address_report and nl_home_basic in the family, an explicit "use X instead when..." statement is the missing piece.

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