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

Goes well beyond the annotations by disclosing the billing model: one trial address or one credit per unique address, no charge for repeat lookups within 7 days, empty answers, or errors. It also states the authentication requirement (trial_code unless signed in or an API key is configured), which the annotations do not cover.

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?

Front-loads what is returned, then the cost model, then the eligibility caveat, with no filler. The middle sentence is dense and carries several clauses, but every clause conveys distinct billing or usage information.

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 two-parameter lookup with no output schema, the description covers return content ('WOZ values ... for all available years'), the matched-address caveat, cost, and auth. It does not sketch the shape of the returned value beyond 'values', which is a minor gap given no output schema exists.

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 both parameters are already documented with format examples and the trial_code fallback rule. The description reinforces the trial_code condition but adds no syntax or meaning the schema lacks, so the baseline of 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 ('Returns the WOZ values of one Dutch address for all available years') and pins down scope ('with the address as matched'). This is unmistakably the data-lookup tool among siblings that otherwise deal with trials, payments, balances, and address lists.

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 a clear usage boundary ('For questions about properties, not to assess or profile people') and the cost/eligibility conditions, including when calls are free. It stops short of naming alternatives, though no sibling performs the same lookup, so there is little to route against.

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