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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that: the one-year window, the aggregation semantics per property type, and the fact that recent sales carry links to separate valuation records. It stops short of stating result counts, ordering, or coverage limits.

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 opens with the resource and scope and then enumerates the returned aggregates. Almost every clause earns its place; the trailing 'with links to their own valuations' phrasing is slightly convoluted but still informative.

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 correctly carries the return-value burden by listing exactly which metrics come back. Safety traits are covered by annotations, and the only parameter is fully documented in the schema, so nothing essential for calling this tool correctly is missing.

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?

Only one parameter, and the schema already documents it fully (four-digit pattern, example "2200") at 100% coverage, so the baseline is 3. The description's contribution is limited to confirming the Danish postcode domain, adding no format or edge-case 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?

The description names a precise resource (registered home sales), a concrete scope (a Danish postcode, past year) and an explicit breakdown (per property type: count, median price, median price per m², most recent sales). It is immediately distinguishable from get_valuation and search_address, though it never names a sibling to reinforce the boundary.

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?

Usage is implied through the temporal scope 'over the past year' and the postcode granularity, which tell an agent what question this tool answers. However, there is no explicit when-to-use, when-not-to-use, or routing against get_valuation (which the 'links to their own valuations' clause gestures at but does not resolve).

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