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

With no annotations, the description carries the full burden, and it does disclose two useful traits: the 1-credit cost and the shape of the returned data (price, index, annual change). It says nothing about whether the call is read-only (inferable from the resource), error behaviour for an unrecognised slug, or how the 'latest' month is determined.

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 tightly packed sentence with the resource, measures, granularity and scope front-loaded, followed by slug examples and the cost. No filler, nothing repeated from the schema.

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 simple two-parameter read tool with no output schema, the description is close to sufficient: it states what comes back, what geography means, and the cost. The remaining gap is the semantics of 'months' (window size, ordering, default when omitted).

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 nominally 100%, but the schema text is effectively empty ('string', 'number 1-120'), so the description does real work by explaining that 'area' is a slug and giving three concrete examples at different geographic levels. It leaves 'months' unexplained beyond the schema's 1-120 range, so it does not fully compensate for both parameters.

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 the specific dataset (UK HPI) and the three returned measures (average price, index, annual change), with the granularity (by month) and the geographic scope (country, region or local authority). This separates it from siblings such as price_paid or ons_timeseries, though it never explicitly contrasts itself with 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 by the geographic scope and slug examples, making it obvious this is the tool for UK house price statistics. There is no explicit when-to-use guidance, no statement of when to prefer price_paid or ons_timeseries, and no mention of data lag or coverage limits.

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