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

With no annotations, the description carries the burden and does substantial work: it discloses that access is free with no key, the data source (HM Land Registry Price Paid Data), the geographic scope, the comparison window, and the 30+ sales-per-period threshold that filters results. It stops short of describing failure modes, caching/freshness beyond the 6-month window, or the shape of the returned lists.

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 the key constraint ('FREE, no key') and then packs methodology into a tight sentence; every clause about window, median, and sales threshold earns its place. The trailing 'Also GET /drops/price-moves (JSON) or ?format=text' is slightly wasteful and confusing, since the schema exposes no format parameter and this tool presumably wraps that endpoint already.

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 read tool with no output schema, the description is nearly sufficient: it says what is compared, over what period, filtered how, and from what source. The remaining gap is the `direction` enum and how the risers/fallers lists are structured in the response, neither of which is covered anywhere.

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 50%: `limit` is documented in the schema (default 10, max 25) while `direction` (both/risers/fallers) has no description at all. The description's phrase 'top risers and fallers' partially illuminates what `direction` selects, but it never names the parameter or explains that 'both' is the default, so it only half-compensates for the gap.

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+resource: the biggest house price moves by postcode district, including the exact metric (median sold price, latest 6 complete months vs same months a year earlier) and coverage (England & Wales). It does not distinguish itself from the sibling pack tools (area_comps_pack, price_paid_pack, price_paid_discover), so an agent has no basis in the description for choosing among them.

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 rather than stated: an agent can infer this is for ranking districts by price change, and the 30+ sales filter quietly tells it this is a statistical comparison rather than raw listings. There is no explicit when-to-use, when-not-to-use, or reference to alternatives among the sibling tools.

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