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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the description only needs to add operational context. It usefully adds that the latest quarter is often provisional and that calls cost 1 credit, but says nothing about response ordering, country coverage limits per call, or error behavior for unsupported geos.

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-loaded with the metric and scope, then caveats, then cost; every clause adds information. The audience clause ('for buyers, movers and investors') is the one mildly decorative element.

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 does enough: it establishes that output is a quarterly series of annual % changes, that levels are not returned, and that the newest point may be revised. A brief note on result shape (e.g., rows of period plus value) would close the remaining gap.

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 100%, so the baseline is 3. The description reinforces the dwellType default ('all dwellings (default), new or existing') and implies that n counts quarters ('quarter by quarter', 'latest quarter'), but adds no syntax or edge-case guidance beyond the schema's own parameter descriptions.

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 metric (annual % change in house prices), a specific unit of observation (one European country, quarter by quarter), and a scope filter (all/new/existing dwellings). The Eurostat prc_hpi_q source and the 'European country' constraint implicitly separate it from the sibling house_price_index without needing to name it.

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 concrete usage context ("are house prices rising in Portugal or the Netherlands", for buyers, movers and investors) and an explicit limitation that it returns rates of change, not euro prices, which steers the agent away from using it for price-level questions. It stops short of naming an alternative tool for price levels or citing a named sibling.

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