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

Annotations already declare this a safe, idempotent, closed-world read, so the description's job is to add substance — and it does: it discloses the upstream data source, the 1995 coverage boundary, and the non-obvious caveat that price per square metre is computed on the home's *current* EPC floor area rather than historical area. It does not address empty results (a home with no recorded sales) or any rate/size limits, which keeps it from a 5.

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 purpose and scope are front-loaded, and the returned-field list is packed into a single dense sentence with no filler. It is slightly heavy to parse — a field list this long reads better as a short clause sequence — but nothing is redundant.

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 carries the burden of explaining return values and does so thoroughly: price, month/year, derived price per m², and first-to-last change. The main gap is behaviour for a home with no recorded sales, which an agent calling this on an arbitrary akey would want to know.

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?

The single akey parameter is fully documented in the schema, including its hex pattern and its provenance from search_addresses. The description adds nothing about the parameter itself, so the baseline 3 for high schema coverage 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 resource (every recorded sale of one home), a concrete scope (since 1995), and the data source (HM Land Registry price paid data), then enumerates the returned facts. It also explicitly contrasts itself with address_report, so an agent can distinguish the two without opening either schema.

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 closing clause 'The short answer to "what did this house sell for"; address_report has the rest' gives a clear routing rule and names the alternative for broader needs. It stops short of a full when/when-not statement (e.g. that the home must first be resolved via search_addresses), but the split of responsibility is unambiguous.

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